Mouse for DECstation 5000 series, SERIAL.bus, in unknown but probably working condition.

It's probably been something like 20 years since I had a system that I could plug this into.  I didn't even know I still had these mice, and probably had them confused with HP-HIL (the AMP SDL connector looks similar, maybe even identical.)  Found these while looking for something else, as is typically the way of such things.

As you might expect, completely untested.  I don't know what systems this is compatible with -- the manual for the DECsystem 5000 mentions this mouse, but it may not work with all such systems, and it may work with other systems not mentioned.  Physical condition is good, as pictured.

Price is per mouse.