My friend had one too. And it did as you said, basically dumped memory to disk and made it bootable. It had a wire with a red button that came out of the case.

We used it for a couple games when one of us had a bought copy and one of the various copy programs didn’t work (I had a disk full of them being young and broke)

Worked well for arcade games. Didn’t work well for games that loaded more stuff from disk..