Hey all! I've seen confusion about how labels should look for GBA cartridges, so I've decided to show at least one example from each region I own and write the differences between them. Unfortunately, I do not have a normal Japanese cartridge ready so they are absent from this comparison.

Super Mario Advance is a Brazilian cartridge. The Incredibles is an American cartridge. Tony Hawk's Underground 2 is an European cartridge.

American cartridges will contain an ESRB age rating in the corner, a serial number ending in USA, and a number indented directly through the label into the plastic - it's hard to see in most photos, but it's there if you look in person or zoom in.

Brazilian cartridges are similar to American, but their ESRB rating equivalent is in Portuguese. Curiously... They lack the indented numbers and have no serial printed into the label, but they come with an ID sticker attached to the back and a sticker containing the same ID inside the cartridge, so you can verify both the label and PCB match.

European cartridges do not have an ESRB rating, their serial numbers will end with specific local codes (like UK) and they will have a C E logo. They also have the indented numbers to identify original stamps.

So good signs your cartridge is a fake is: it lacks the indented number but it isn't a Brazilian cartridge. It mixes and matches the C E logo, ESRB rating or serial number from a different region.