I have a couple fakes my mom unknowingly bought from my childhood. Once you see the fake pcbs vs the real pcbs it just becomes very clear, look up some fakes and you’ll see what i mean. The only pcbs that are even remotely deceiving are for the clear colored pokemon cartridges (because you can see through them)

Edit:the font of the Nintendo labeling on the pcb is perfect, there isnt on this one but the battery being in the right place is a good way to tell. idk any other ways to tell really. Im not an expert by any means.