Help needed to identify component

[JoeG]

I have several of the "VIC-20 MULTI USE PROJECT TEST CARTRIDGE" boards, and I'd like to use one to build a cartridge that can provide numerous games via EEPROM.

I've attached several photos.
- The first is of the bare board
- The second is of the cartridge that I would like to build
- The final photo is of a component that I'm not familiar with. I'm guessing it's some form of a switch, but I don't know what it's called.

Any ideas?

Thank you!

Joe