Earliest PC arcade emulation?

I was thinking when arcade emulators first came around for PCs. My earliest memory is around 1988 I downloaded Robotron 2084 as a standalone game from a BBS that I thought was something adapted for the pc from the original but it was the actual arcade version of Robotron.

I'm wondering about the first emulators, if anyone has any stories. I assume, like Robotron, they were baked into the roms as one .exe file and offered as one-offs for each game.