Which format is the barcode around the ring? It looks like a Code 39 variant, in that there are only narrow (1 pixel) and wide (3 pixel) lines and spaces, except that they make no sense when put together (e.g. it's not A-Z/0-9 characters, merely binary data). Additionally, each wide bar is preceded by a narrow space; each narrow bar is preceded by a wide space. PS2 CD-ROMs also have a second barcode in the ringcode area which isn't present on PS2 DVDs.
Or are the spaces ignored entirely with narrow bars being 0 and wide being 1? With no spaces, CDs are 104 bits long, DVDs are 108 bits long. The second barcode (PS2 CDs only) is 28 bits long.
I can't find anything on Redump about the PSX BCA mark or whatever it is called. The same barcodes are also on PS2/PS3 and even audio CDs and DVD videos, anything on Sony-pressed discs.
There are ringcodes on regular black-backed PlayStation CDs! To be able to read the ringcodes of non-Platinum discs (e.g. the majority of PlayStation games out there), you will need any device capable of "red" light output (or orange, yellow etc). For example, incandescent bulbs (lamps, flashlights etc.), infra-red light (e.g. remote controls) or even sunlight. Digital image capture devices can see infra-red light, thus pointing even a TV remote's infra-red LED at the disc should show up on your camera. It may take a while to find the data, but it should show up as black numbers on a solid red background - the inverse is true about the barcode.
Alternatively, if you have a powerful enough light source and a scanner, you can simply shine the light straight through the picture side of the disc while scanning, however the mould SID code may not show up in the scan due to the amount of light. It is advised to shine the flashlight from an angle, so the light doesn't overpower the scanner and whitewash everything (sitting the flashlight right on top of the disc made my scanner show a glitched area over parts of the ringcode, making the image useless).
Light which uses the blue spectrum (e.g. "white" LEDs and flourescent lights including CFLs) will not work.
PAL version discs have the same style of ringcodes as per PS2 and later games, but with one of three varying logos. Games made up to 1998 (including Tekken 3) have a DADC AUSTRIA logo, games from 1998-1999 have DADC without the Austria part, and games from 2000 onwards have Sony DADC, the same as PS2 games.
Note that the Sony DADC number is not PlayStation-specific and is used for all discs made at that factory (at least on the machines which use this numbering format), including audio CDs, DVDs, UMDs and Blu-Ray discs, and also cannot be used to determine the age or release era of a disc, for example movie DVDs from the early 2000s seemingly start at zero yet PSX launch titles from way back in 1995 start at roughly 170000 (e.g. Tekken 1 is A0000173745-0101). The same pressings will always use the same DADC serial number, although the SID code and the two trailing digits (e.g. IFPI L555 and the "15") can change on rare occasions. An updated/bug-fixed release of the same game will always have a different DADC number even if the SCES/SLES number is exactly the same on the label.
The standard Sony DADC format used on PS1 games is decoded as such:
A01xxxxxxxx-yyzz. X is the unique disc pressing number, Y is the disc number in the series and Z is how many discs are in the series. Games which span multiple discs use the same serial number, for example the two discs of Resident Evil 2 (the standard English language version) are numbered A0100241992-0102 and A0100241992-0202 respectively (and the ringcodes are not listed in the database at all, sigh).
The earliest discs (note the above Tekken 1 example) start with A00 instead of A01, I do not know what the 0 or 1 means (some DVDs also start with A00; the DVD5 top layer blank used for making single-layer discs on dual-layer equipment starts with A09 and is invariably A0900555555-B511, while the UMD blank layer is A0600666666-B511).
Speaking of DVDs, the four-digit suffix format is different due to taking into account dual-layer discs. A511 means A-side (layer 0/media side), DVD5 (single-layer), disc 1 of 1. B923 on the other hand means B-side (layer 1/label side), DVD9 (dual-layer), disc 2 of 3. This format, including the 5/9 for the single/dual layer disc types is also used on UMD and Blu-Ray discs, even though they are not called 'DVD5' or 'DVD9' in their own formats (e.g. Blu-Ray is BD25 or BD50).
Note: Some PAL version discs (usually the generic demo disc releases with PBPX serials) are manufactured in Japan and have a Japanese style ringcode where the ringcode reflects the serial number, and will invariably have a SID code of IFPI L27x (instead of L55x) and a mould SID code of IFPI 45xx in place of 94xx (Europe) or 65xx (Australia).
NTSC U/C discs have no manufacturer logo, but use a serial number similar to PSRM-nnnnn followed by a two-digit number. Unlike PAL discs, the last digit of this number does not correspond to the SID code's last digit. The same serial number is also in the small print on the CD itself. Not all games may use the letters PSRM. Most NTSC discs have a series of symbols after the ringcode such as ☼ ☼☼ ☼☼☼☼☼☼☼☼. It is unknown what these represent.
Japanese discs are similar to NTSC U/C except that they simply use the SLPS number (or similar letter code) in place of the PSRM number (note that this number may not always correspond to the disc ID e.g. PlayStation The Best re-releases are in the 90000 range yet the ringcode will still be a standard low number such as SLPS-00040 if it's the same old pressing as the original); the hyphen after SLPS etc. is always in the ringcode even if it is not on the disc label.