> You were lucky it wasn't an even older Mouse Systems bus mouse. I'm not sure any kind of adaptor ever existed for those other than the 8-bit ISA card it plugged into :-)
> (Or even older mice with OEM connections/protocols for anything from BBC Mcro, Amiga, ST or any of the many other unique "personal computers" that used mice in one form or another)
Those weren't necessarily older, but contemporary.
The Mouse Systems bus never really caught on, and RS232 mice became the standard, later to be replaced by PS/2 and then USB.
The home computers of the 1980s did often not have a standard serial port, so the mice had to be different, usually connected to a joystick port or similar.
I've still got all kinds of mice somewhere in a box, next to the Centronics printer cables and the 5.25" floppy drives. :-)