So how do you get a 25 year old Atari STM1 Mouse working on a modern PC?
Rip out these guts.
Took a Microsoft Optical USB Mouse, and hacked and glued the optical window into the "ball hole".
Trimmed the old PCB, so we can utilize the original button switches. Trimmed the new PCB so it'll fit inside.
Soldered wiring from the old PCB's buttons to the new USB PCB.
Jam it all back together... AND...
The original Atari mouse is NOT serial. its a proprietary connection utilizing the DB9 connector. So a USB/serial adapter does not work in this case.