The RM Nimbus PC-186 mouse predates the serial/USB era and actually transmits raw data regarding its position, known as quadrature. The port on the back of the PC-186 is not a serial port but a dedicated Mouse/Joystick port.

At the time of launch in 1985 the Mouse was an option extra, priced at £87!


Here we show the teardown of a Logitech 2F-RM



Here are some additional examples of the Nimbus Mouse