I found a N64 at a thrift shop today. It was in very good condition and came with Mario 64. When I opened it to clean it, which I always do when I get a new system, I noticed it had a clear green cartridge slot
(you know, part you can only see if you hold open the little doors, also the part you cut as part of making it region free.)
The system didn't appear to have ever been open before since it still had the sticker on the expansion slot and the screws seemed untouched. Any idea how this happened?