Pokémon Leaf Green Authenticity Check

Reposting here as previous post was removed by the moderators Hi!

I’ve recently sold a Pokémon leaf green cartridge, and my buyer is having doubts that it might not be the real deal.

I purchased it over ten years ago second hand, so I can’t check with the seller and was wondering if anyone on here can help me authenticate it, and could you let me know how I can spot if a cartridge is a fake? Any advice will be useful!

Thank you!