SONIC 2 Sega Game Gear/Mega Drive games all have different numbers on the boxes, manuals and cartridges. I don't know the official term for them - model numbers, asset numbers? They also have catalog numbers on the boxes. This is the cartridge scan we have for the JP Game Gear Sonic 2 on SonicRetro: 670-2660-01 This is the cartridge scan that SMSPower has: 670-2660 Usually the cartridges codes are just 7 digits (670-xxxx), so the -01 implies a revision. This cartridge label is unusual, because it also has the catalog number (G-3321), which is usually only printed on the spines of Game Gear game boxes. Sonic 2 also got a Meisaku Collection release and Meisaku Collection releases have different catalog numbers (G-3338 in Sonic 2's case). So the Meisaku Collection would have required a different cartridge label. After looking at a few auction sites: You'll need to zoom in, but sure enough the original box release has the 670-2660 cartridge and the Meisaku Collection has the 670-2660-01 cartridge. HOWEVER, would a new cartridge label be enough for a revised number? Or does it also imply a revision to the game (bug fixes etc.)? Essentially, do we have ROM dumps of both cartridge versions, and are they identical? SONIC 1 So here's a little bit of trivia. The JP Game Gear Sonic 1 cartridge had two different labels. But both versions have the the 670-1947 code. Full details here: https://twitter.com/YmPXden33UUYCF3/status/1094031222567628801 Basically, the original version accidentally had a 2 Player logo on it. The comments section says that the 2 Player logo was covered up with a white sticker (which is what we have on SonicRetro - and we have the corrected label version for the Meisaku Collection release). This raises a few questions: 1. Did any stickerless versions of the "2 Player" version make it into the wild? 2. Was the corrected version specific to Sonic 1's Meisaku Collection release, or did the original box version ever ship with the revised cartridge label? 3. How should we cover the "2 Player" version on SonicRetro? Would we want scans both with the white sticker on and with the white sticker peeled off? 4. Why does the corrected label have the exact same code? Why is it 670-1947 and not 670-1947-01? Does it not count as a true label revision, because the first one was an error, or is -01 only added to ROM revisions? Also, just as a general question, does anyone know the methodology for how those last four digits were assigned? It seems the later the release, the higher the number, but by the time they got to G Sonic they were up to 670-9587.