Similar to HD DVD with HDi menus (Microsoft changed that from iHD late in the game to avoid any possible association with Apple...
), any Blu-ray disc with Java menus will have a unique ID. It's in the CERTIFICATE folder, in a file called ID.BDMV, and it's in two parts:
Using a hex editor on this file, the 4 bytes located at hex address 28-2B represent the 8-digit Organization ID (which is, usually, the same for every title released by a studio), and usually begins with 7FFF. The 8 digits can only by hex digits (0-9, A-F)
The next 16 bytes represent the 32 character Disc ID, which can be randomly generated, or just completely made up (by the studio, of course). Sometimes there's text 'hidden' there (again, the 32 digits are only hex characters, but 16 standard characters they represent my spell out words), or sometimes all zeros except for a small number at the end (like 00000000000000000000000000000012, most likely the 12th Blu-ray that studio made).
If the ID.BDMV file exists, the 20 character value starting at hex location 28 will be unique to that disc (check to make sure it has a value though, and not all completely zeros...). I'm pretty sure all Java titles will have an ID file, but for the most part, HDMV only titles will not...
Visual aid:
Organization ID is 7F FF 0B B8
Unique Disc ID is 00 00 00 00 00 00 4C 57 57 2D 31 4E 2D 4E 45 31
Notice also that the Disc ID happens to spell out LWW-1N-NE1 on the right side. This is the title code and region code for this disc that this studio uses, but this isn't always the case. Sometimes it's just 32 'random' hex characters.