What if I told you that the Blu-ray you know and love was not the *original *Blu-ray? The Blu-ray that came onto the market almost 20 years ago in mid-2006 was, essentially, round-two for the technology which first launched as early as 2002-2003 in Japan, at around the time that HD-DVD (formerly Advanced Optical Disc) was being conceived. As the home of Sony, TDK and Pioneer, Japan often had the cutting edge when it came to optical disc technology with some of these never quite finding international success.

A Sheltered Life

It turns out that Blu-ray traces its heritage to around 1998 when the first viable blue-laser diodes became available and were looking for applications. For professional storage library applications, an extension of the Magneto-Optical style 130mm cartridges were made in the form of UDO and UDO2 (short for Ultra Density Optical).

But a second project produced what would become the predecessor to Blu-ray, DVR Blue. A prototype of DVR Blue was demonstrated in 2000 with a claimed 22.5GB capacity and later, more marketable units were showcased in CEATEC in 2001. It would not be until 2002 that the format gained the Blu-ray name.

It was around this time I would have first heard about Blu-ray and its astronomical (for the time) capacity. I recall seeing it on the television news, in its original guise, which involved a cartridge. I believe the reporter was a bit skeptical about formats using cartridges as being old-fashioned, bulky and perhaps unlikely to succeed. Looking back, the reporter was probably not wrong.

The discs were re-recordable and had a claimed capacity of 23GB in fully enclosed cartridges. Examples include the TDK BD-RE120N and Maxell BDF120. Each disc had an ID code for inventory and was suitable for recording Japanese HD broadcast satellite TV that required copy protection. In August 2003, the discs were 2880 JPY to 3180 JPY individually but with an RRP of 3600 JPY.

Its success would be considered quite limited, but perhaps not forgotten, as I was able to track down a relic which inspired the creation of this post. But what really paved the way for Blu-ray to escape its cartridged life was the development of hard coatings in around 2004 which were essential to ensure the 0.1mm overcoat did not become damaged through regular bare-disc handling. To that end, TDK’s Durabis (and later, Durabis 2) coating was one well-known solution that allowed for TDK to start selling bare discs by 2005 with the familiar 25/50GB capacities. It’s interesting to note that recordable-erasable (or rewritable) discs came first in Blu-ray, with the write-once recordable discs only becoming part of the specifications at the time when bare discs became widely available.

A Half-Way House?

While browsing my favourite source of Japanese odds-and-sods, I came across a listing for a TDK BD-RE135N and I just knew I had to have it. It was not the “ancestral” Blu-ray that was fully cartridged, but perhaps a slightly lesser-known beast.

This disc came shrink-wrapped, new-old stock that had never been used.

The disc is a half-way house between cartridged and open Blu-ray. Introduced in November 2004, this disc has an open cartridge design where the disc is non-removable. Rather than the 23GB commonly quoted on the older enclosed cartridges, this one boasts a more familiar 25GB capacity and is aimed at video applications including recording Japanese high-definition broadcast satellite.

The disc is Made in Japan by TDK and works with copy protection system (CPS), likely a CPRM equivalent for Blu-ray. The disc complies with BD-RE Ver 1.0 specifications. To ensure it survives in its semi-open form, it is hard-coated, but likely with an earlier form of hard coating (the original version of Durabis perhaps, but I couldn’t identify any such indications). The barcode number is 4906933524636.

The outer sleeve was quite a nice design, having silver accents making it look and feel futuristic. It was pretty state-of-the-art for its time.

The wrap-around cardboard leaves the edges of the library case exposed, showing the edge of the insert that acts as a spine label and the side of the case where users can grasp to open it.

From the outside, the case is a smoked grey colour with translucent clear and matte finishes.

The insert card only runs part-way up the case, held inside a plastic pocket that wrap around the spine and the rear of the case, leaving the front untouched.

The semi-open cartridge is held up from the sides of the case and is safely clipped into place.

A label sheet is provided and is placed behind the cartridge.

The semi-open cartridge exposes the disc on the top, but with an ovular window that doesn’t let the disc escape (at least, not without dangerously bending it). The disc is held in place by small tangs on the rear shutter mechanism which keeps the disc from shaking about in the cartridge when the shutter is closed. With such a large area of disc exposed and plain white, I suspect users would label their discs with markers directly – given the data layer is very much on the opposite side, this would seem like a safe thing to do.

The underside of the cartridge is simple – aside from some location and detection holes, it has a covered opening where the laser pick-up and spindle access the disc and a labelling area. It’s a bit inconvenient that the label is on the underside of the cartridge! Unlike DVD-RAM, the cartridge appears designed only for single-sided loading.

The front side of the cartridge is curved and has an indent to allow the slot to be fully opened and provide the best access to the pick-up head.

There is a latch button on the right side (as viewed from the top) that releases the shutter cover mechanism drive which is the notch that is near the middle of this edge. Moving that towards the left of the image reveals gears which allow for the shutter to be fully driven open.

The left side edge only has locating slots and notches.

The bottom edge has the write-protect slider and can accommodate a thin label, similar with DVD-RAM cartridges.

The included insert has an interesting inverted colour arrangement for the front and back and is used to index the contents of the disc.

Labels are provided, which can be used on the edge or in the dedicated labelling area on the underside of the cartridge.

The rear of the label sheet has some information about the copy protection system, the write protect notch, recording capacities and the type of disc.

The disc itself is never meant to leave the cartridge. Unlike DVD-RAM, the cartridge is not designed to be removed at all and is rather sturdily sealed shut. I did manage to extract the disc, but at the risk of destroying it, for this examination. The scanned image of the disc is above showing the mostly blank printable-like top coating which is likely able to be labelled with a marker pen. The underside is a familiar BD-RE light brown but the scanner simply picks up most Blu-ray discs as a dark colour.

This is what the cartridge looks like when there is no disc in it. The shutter mechanism is made of two pieces which appear to pivot away from one another when the locking ring is driven. My best guess is that the cartridge would be assembled from the top, the disc inserted and the cover plate at the bottom of the image is installed and bonded to the cartridge to keep the disc captive.

The disc, as seen by my DSLR. This one has been written by the experiment detailed later in this post – unwritten, it is a brighter coppery brown.

The stamping code, as viewed from the top – lots of zeroes! It says “0000000000 BD-RE 6831B3 000000000”.

Sony Professional Disc – Blu-ray’s Cousin?

Whilst researching the fully cartridged Blu-ray, I realised that it looked like something I’ve seen before – the Sony Professional Disc format. This is a recordable-eraseable cartridge blue-laser format used for professional video acquisition and interchange, sometimes known as an XDCAM disc. Used predominantly by Sony equipment, it is available as a 23GB single-layer, 50GB dual-layer, 100GB triple-layer and 128GB write-once quadruple-layer variant. The capacities definitely line-up with Blu-ray – with 23GB being the earliest revision. Superficially, it also looks like the cartridged variant of Blu-ray and has familiar capacity points, but it is said that the Professional Disc system is not Blu-ray. Perhaps it is Blu-ray’s cousin?

As these cartridges are for professional use, they are not cheap to acquire. As a result, I had to acquire some second-hand sets and clean them up for this post – excluding the triple-layer and quad-layer discs which are rare to find at a reasonable price. In my case, some of these cartridges came from Pilgrim Media Group, part of Lionsgate, with the cartridges apparently blanked before resale.

Single-Layer

The disc is stored inside a translucent clear plastic case with space on all sides. Internally, clips suspend the cartridge in the case and keep it in place. The front has a clear window surrounded by matte finish plastic.

The rear is more matte, with there being a plastic pocket that stretches from the rear …

… around the edge to hold an insert that can be used to index the contents of the disc with some text visible on the spine once shelved, just as in the Blu-ray example.

The top of the disc has a dark grey-purple clear plastic with a striking matte and gloss contrast. The printing has the Sony branding, Professional Disc logo, rewritable capability and 23GB capacity with 2.4x speed.

The underside is a dark navy blue. The casing is held together by eight screws, with a full-length shutter along the middle of the disc. There are detection holes and locating slots. A barcode number is printed on the back for tracing of discs and management of disc libraries.

The front edge of the cartridge is curved and the slot extends right to the edge.

The right-side edge as viewed from the top is home to the latch button that unlocks the shutter mechanism and the slots and teeth that allow the shutter to be driven open or closed.

Meanwhile, this side is relatively featureless except for locating slots and notches.

The bottom edge has a write-protect slider and two small labelling areas either side of the slot which also emerges out of this end.

My scanner doesn’t see much when it scans these discs – a dark murky electric blue on the top and a nearly-black brown on the bottom. I suppose it’s down to the reflectivity and angle of the light.

Under natural light and with a DSLR camera, the top is seen as silver (unprinted substrate) while the underside has a familiar BD-RE deep brown.

The disc has a stamping code of PDS-0006.

In the bright area is a BCA barcode. Despite being second hand, these discs did come with clean unused examples of their original inserts and label sheets.

The majority of the discs came with this insert, indicating they were PFD23A discs, what I would consider an ordinary type of disc. It is marked with the XDCAM logo and supports 2.4x speed. It has a 23GB capacity and claims to be formatted – but it appears that sometimes this particular type of disc was not formatted. The rear of the insert can be used for indexing, with the edge of the card folding over the spine so it can be read even when the cases are kept on a shelf.

I also received a sleeve for a PFD23AX, a later revision which seems only to differ by being pre-formatted – but because my discs were all second hand, there’s a good chance that all my discs are actually PFD23As just in the wrong cases.

The included label sheets were never used on this production, but are the intended way to label the cartridges in the three areas designated for labelling – a dimple on the lower left of the top side, the main labelling area in the centre, and a pair of edge labels either side of the door mechanism on the lower edge. The first variant of labels is particularly colourful on the main labels with precautions and other information printed on the rear.

A second, less colourful variety with no HD logo on it, presumably an older design – but I did also find a variant of the printing on the back in my set of discs …

… so it seems that what you get may vary depending on the market the discs were purchased in.

Dual-Layer

The second type is the dual-layer disc which, as it was purchased second hand, unfortunately did not come with any label sheets or inserts. The cartridge and its case is what I received (along with a load of label residue which I cleaned up).

For a blue-laser disc descended from Blu-ray’s common ancestor, it would seem that the choice of a maroon red for this cartridge is a bit out-of-place. It almost seems a bit HD-DVD-like. Nevertheless, the cartridge takes the same form, but now indicates it has a 50GB capacity and is Dual Layer (DL =). The speed is the same and the cover still has a nice contrast between glossy and matte finishes.

The bottom half of the shell remains a dark blue and is barcoded for tracking. There is one additional hole on the right side of the case above the write protect slider, presumably to indicate the dual-layer nature of the disc to the deck.

The leading edge is curved, with the shutter opening up right to the edge.

Along one edge is the white button that releases the latch that keeps the shutter mechanism from actuating. Below that is the slot and teeth that allow the shutter mechanism to be driven.

The other side has a locating notch but is otherwise feature-less.

The bottom edge of the spine has two small labelling areas and a write protect slider.

Similarly to the single-layer example, the scanner doesn’t do a good job of reproducing the actual appearance of the disc.

A photo from the DSLR shows an unprinted silver-looking top and a lighter familiar BD-RE brown on the underside.

Stamper code for Layer 0 as seen from the top reads “PDD-1006-L0-1”.

The code for Layer 1 as seen from the underside reads “PDD-2021-L1-1”.

Teardown – Professional Disc Cartridge

As the semi-open Blu-ray cartridge was sealed and I didn’t want to destroy it, I couldn’t take that one apart. But the Professional Disc, using screws to hold it together, could be disassembled for examination without permanent harm.

Removal of all screws and pressing the latch slightly allows for both halves to separate. The disc was removed to reveal the top cover which contains a spindle clamp to rest on top of the disc once loaded. The rear shutter assembly is shown in the fully closed position to the right.

The rear cover of the professional disc with the shutter in the fully open position. The two halves of the case are joined by the ring and front cover when fully open like this. Without the front cover, it feels very floppy and disconnected.

The shutter seems to be driven from the edge, which has larger slots at either end of travel separated by a raised blank section and teeth in the middle. It might have been simpler to have teeth all the way around, but perhaps is was a design feature to avoid accidental opening.

The “leaves” which cover the opening are somewhat thin pieces of plastic, linked by pivot pins and guide channels in some very intricate arrangement. It can get a little tricky to assemble and is hard to intuitively gasp. Somehow, the old simple sliding shutter like the sort on magneto-optical cartridges, DVD-RAM cartridges or floppy discs just wasn’t enough.

This spring-loaded lever appears to serve as the lock for the shutter, engaging with the toothed/slotted portion of the ring.

A Visual Comparison – Blu-ray vs Professional Disc

At a glance, the resemblance between formats is definitely apparent.

The write protect switch mechanism is located in the same corner of the cartridge, although some of the holes on the underside are different.

Had I a sealed-cartridge example of early BD-RE, I guess it would be even more similar to the Professional Disc. The outline, however, is pretty much identical, but with the semi-open cartridge design, the top surface is accessible for labelling and the disc is coated to resist dust. The spindle clamp is not included in such a cartridge, instead, the shutter serves to hold the disc at the centre instead.

Perhaps the biggest difference is the sensing hole locations and the lack of screws in the semi-open cartridge design.

Instead of a full-width opening, the shutter only opens one side, with an area on the other that can be used for labelling. This design for Professional Disc applications lends itself to dual-pickup head applications for write+verify without slow-down, or for faster multiple-access for editing applications. The advertised speed is 72Mbit/s on a single head and 144Mbit/s on a dual head deck, but interestingly, some batches of PFD23AX discs were defective due to deformation causing issues with insert editing but otherwise recording and playing normally. Meanwhile, the Blu-ray BD-RE was 1x, later 2x, rather than the DVD+R-like oddball choice of 2.4x that the Professional Disc has.

Even the outer plastic cases share the same dimensions …

… and practically the same thickness. It is seemingly no coincidence – I would say that Professional Disc perhaps branched off DVR Blue or Blu-ray right at its early full-cartridge incarnation, just in some incompatible way. I guess this helps segment your market because professional users can afford to pay more, right?

The three discs together …

… not the same … but not that different …

… relatives of one another, separated by market segment, specification differences and time.

Read/Write Compatibility

Given all of these cartridges, are any of them interchangeable with the bare-disc Blu-ray drives that we know and love? That’s a question I’ve always had on my mind. To do this required removal of the discs. For the Professional Discs, this was easily achieved by unscrewing the cartridge allowing both halves to separate. For the Blu-ray, however, I needed to do some very careful bending to slip the disc out of the cartridge without snapping the substrate. Unfortunately, one attempt did not go so well, leaving a hairline crack in the hub, but the other was successful. Alternatively, one could just cut through the sealed cartridge plastic but I didn’t want to damage it.

BD-RE V1.0

On a technical basis, all the Blu-ray discs would have been either Blu-ray Recordable Ver 1.0 or Recordable Erasable Ver 2.0 or newer types. As a result, a BD-RE V1.0 disc, despite being a BD-RE on the surface, may be unrecognisable to modern drives. Indeed, this seems to be the case at least with some drives.

The LG BH10LS30 is unable to recognise the presence of any medium. The Lite-On iHBS212 is able to recognise the disc with no Media ID (this seems to be accurate). Interestingly, DVD Identifier complains regarding the recording speeds due to unknown DI Count (presumably that’s short for disc information?).

Both the TSST SE-506CB slim-drive and the LG WH16NS58 are able to recognise the media. But just because these drives recognise the media does not mean they can write to it.

The LG GGW-H20L is not able to recognise the media at all – either before or after writing.

But my Pioneer BDR-X13JBK is unable to recognise the media correctly with an “Incompatible medium installed” error, but can recognise it after it is written. Being a recordable-erasable medium, I decided to see if the BDR-X13JBK could erase it …

… but it fails with a “Medium Format Corrupted” error. So it seems that the Ver 1.0 media is a bit of a curveball for all the drives I still possess.

The media code block is as follows:

----------------------------------------------------------------------------
Unique Disc Identifier : [BD-RE-SL:NO_ID_PRESENT-???-000]
----------------------------------------------------------------------------
Disc Type :              [BD-RE SL : Class 0 - Version 1]
Manufacturer Name :      [Manufacturer Not Found In Database]
Manufacturer ID :        [Not Present On Disc]
Media Type ID :          [Not Present On Disc]
Product Revision :       [000]
Stamper Date :           [Not Present On Disc]
Layer Info :             [1 Layer (L0) : 25.03 GB (23.31 GiB) Per Layer]
Blank Disc Capacity :    [12,219,392 Sectors = 25.03 GB (23.31 GiB)]
Recording Speeds :       [Not Available Due To Unknown DI Count]
----------------------------------------------------------------------------
** INFO : Hex Dump Of 'Media Code'-Block Listed Below
** INFO : 4-Byte Header Preceding 'Media Code'-Block Discarded
** INFO : Format 00h - Disc Information
0000 : 44 49 01 00 01 00 63 00  42 44 57 01 14 01 00 00   DI....c.BDW.....
0010 : 01 00 00 00 00 00 00 00  00 02 00 00 00 19 4e 7e   ..............N~
0020 : 01 ec 64 64 28 28 28 28  1e 1e 1e 1e 00 00 00 00   ..dd((((........
0030 : 4e 69 76 04 04 98 98 24  4e 69 76 04 04 98 98 24   Niv....$Niv....$
0040 : 4e 69 76 04 04 98 98 24  60 06 06 70 00 00 00 00   Niv....$`..p....
0050 : 00 00 00 00 00 00 00 00  0f c0 c8 c8 c0 c8 c8 c0   ................
0060 : c8 c8 00 00 00 00 00 00  00 00 00 00 00 00 00 00   ................
0070 : 00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00   ................
[SNIP - All Null Bytes]
0df0 : 00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00   ................
----------------------------------------------------------------------------
[ DVD Identifier V5.2.0 - http://DVD.Identifier.CDfreaks.com ]
----------------------------------------------------------------------------

I suppose being so early in Blu-ray’s career, there was no need for a media code perhaps – the media code block returned is mostly null.

To write the disc, I gave it to my LG WH16NS58 which managed a 2x write to the disc (the only speed it supported). While there was no speed written on the box itself, based on the spec, it appears that it is a 1x disc.

The write had a few W-OPC dips but the drive itself did not stumble. The burn completed in 43 minutes 34 seconds.

Placing the disc in my very competent Pioneer BDR-X13JBK for a transfer-rate test shows that the disc was a difficult read for the most part, with unrecoverable errors towards the end. Generally speaking, any form of re-writable disc running at the wrong speed is likely to produce a bad recording and this is no exception.

Interestingly, the Lite-On iHBS212 managed to read it all, but very very slowly. That’s the difference a drive with a different chipset can make.

It read correctly but the quality scan shows a level of errors on this disc is quite rare to see except for completely damaged and unreadable discs. So even something like this could read back if you’re patient and lucky.

Unfortunately, this proved to be a one-way ride. Trying to get the WH16NS58 to read its own burn was impossible – it simply refused to recognise the disc after it was burned with an “Incompatible Medium Installed”. This is why I couldn’t run a TRT on the disc on the drive that burned it – the act of burning it turned it into a disc it could no longer accept!

As a result, to try and burn it again, I tried to see if any drive would erase it. I started with the Lite-On iHBS212 but attempting an erase in ODC just resulted in errors.

Imgburn was a bit kinder, managing to interpret the error for me. It seems to suggest that attempting to erase the disc somehow crashed and rebooted the drive’s firmware. I guess that can be explained if the disc’s internal format data is not in the expected format and perhaps some null values are causing the firmware to trip up.

Even when written, the GGW-H20L still won’t recognise it – this time with a “Cause not reportable”. The TSST SE-506CB sees the disc as written, but simply won’t erase it. As a Blu-ray burner, that drive is so incompetent that it couldn’t write a single disc in my experience, let alone erase it. It’s still particularly good at pulling media codes from obsolete formats.

Finally, my Pioneer BDR-X13JBK can recognise the burned disc, but an attempt to erase it results in failure with “Incompatible Format”. As a result, it seems to be pretty much a write-once medium.

I took a second disc just to see what would happen with my iHBS212 as the only other drive that recognised the blank – turns out it wouldn’t write it at all, erroring out during the lead-in phase. So by pure chance, I had chosen the only burner that would write anything and it did a bad job because it simply could not operate at the intended 1x speed.

Single-Layer Professional Disc

Trying to identify a Professional Disc is an interesting exercise. As I received the dual-layer disc first, I knew that my BDR-X13JBK was the one to try. The DVD Identifier software errors out even though it retrieves data because there’s something interesting with the data format that it cannot understand, instead reporting “Unsupported Blu-ray Disc Detected”.

Using ImgBurn, the session data and disc state information is all missing so no writing or reading can take place, but it identifies the MID for this disc as pppppp-`-000. A very odd sequence of bytes if I should say so myself, perhaps because the disc definitions may vary enough from Blu-ray that it might just be reading in something else as the MID. Or maybe they just thought nobody would ever see it. It’s “p” for professional, six times … perhaps that’s why the stamping code is PDS-0006, standing for Professional Disc Sony number 6?

Dual-Layer Professional Disc

I received the dual-layer professional disc first, so I gave it some attention to see what drive would be able to identify it.

The LG WH16NS58? Nope. The Lite-On iHBS212? Nope.

The Lite-On iHBS312? Nope. The LG BH10LS30? Nope.

The TSST SE-506CB? Nope. The LG GGW-H20L? Nope.

But the Pioneer BDR-X13JBK can! It identifies it as having an MID of SONY-XD4-001. Given this disc has a familiar 50GB capacity, it is probably more akin to the Ver 2.1 discs that are most used and the media code is of a human-readable, expected format. But likely due to some disc format differences to keep the formats incompatible, it cannot identify the status of the disc or write capabilities. Unfortunately, this also means this disc cannot be written nor read.

Perhaps this is not entirely the end for the professional discs as the “swap trick” of starting the drive with a supported disc of a similar type so that the disc details are loaded into RAM, sending it to sleep so the spindle stops and sneakily swapping out the disc might lead to some reading or writing. This won’t work if there’s something significantly different (e.g. with the ATIP addressing or other zones of the disc). But as the only drive of mine that seems even somewhat inclined to work with the discs is one of my newest and most beloved, I don’t feel quite like taking it apart, not to mention the risk of laser exposure.

Conclusion

I’d hazard a guess that many may not have known that that Blu-ray started its life inside a cartridge due to the fragility of its 0.1mm overcoat. Thanks to encountering an early open cartridge form of BD-RE disc for sale that straddled the eras, I was sent down the rabbit hole of early Blu-ray, learning that the technology was already developed for sale as early as 2002-2003 in its fully cartridged form. The example shown in this post apparently already had a hard coat in 2004, paving the way for the cartridge-free variety that became more widely available in 2005 and its global launch in 2006. I’ve not come across drives that support this form of Blu-ray, although it seems it was something that didn’t leave Japan in any big way.

The Blu-ray that is bare, free of a cartridge, that launched in the west was essentially Blu-ray Recordable Erasable Version 2.0 (and newer). It is often said that cartridged formats, despite having physical protection benefits, usually are unsuccessful in the consumer market due to its bulk and cost. Eschewing the cartridge, then, was a positive step forward. It was only with the development of hard-coats such as TDK’s Durabis 2 that made cartridge-less Blu-ray possible, while the video format only really took off once a suitable copy-protection scheme in the form of AACS was agreed-upon and integrated into the standard.

It would seem that liberating the disc from a Version 1.0 cartridge results in a disc that few drives can burn. As a 1x medium, the only drive I had that would burn it did so at 2x and produced a bad recording as a result. After writing, some drives that could previously recognise the disc stopped doing so, while the reverse was also true. If the disc were written by its intended equipment, it might be possible that some drives may have been able to read it in some way, although perhaps not be able to parse the BDFS file-system which was specific to video recorders of the time of which little information seems to be available.

It would seem that the timeline for Professional Disc diverged from early Blu-ray, as there was no need for copy protection in those applications. The single-layer capacity matches the 23GB initial capacity of Blu-ray, with 25GB Blu-ray coming later and 27GB Blu-ray being “reserved for future use” but apparently never released. The discs were cartridged for robustness, with a design that is very much similar to the half-enclosed early Blu-ray BD-RE Version 1.0 disc but with a shutter that extends the full length of the case allowing for dual-pick-up drives that increase access speed and provide better editing capabilities. Despite its similarities, it seems the discs themselves have a different data structures describing their physical format and status, resulting in drives either not being able to detect the disc at all or detecting some characteristics but not enough to access the data on the disc (i.e. unknown capacity, session status). So while they seem to share a common technological root, the Professional Disc and early Blu-ray are likely deliberately incompatible variants of one another for market segmentation, both of which are different enough from modern Blu-ray that modern drives do not work with them.

This was not a rabbit-hole I had anticipated going down, but sometimes the circumstances arise and curiosities find answers … hope you too found this interesting!