I'm thinking it's a Japanese 64. But it that were the case wouldn't the games not even fit?
yes but the physical lockout on an n64 is the easiest region-lock to work around. all it takes is breaking off the plastic tabs that match with the security slots in the cartridge, and then you can fit any n64 NTSC cart in there. japanese and north american circuitry for n64 is interchangeable, it's only a physical lockout.