This page
http://www.mouser.com/ProductDetail/Alpha-Wire/2466C-SL002/?qs=oCgOJbGQ3O%252bEmVcYnZ3afg%3D%3D seems to confirm what
lloyd was thinking, as the application notes suggest :
RS-232/422/485, audio systems, computer peripherals, security and control systems !
So, I'm going to presume it came from computer system that was decomissioned in the early 1980's that had serial terminals attached!
The most recent project I used it for was to extend the wires of a
DS18B20+ One Wire Digital Temperature Sensor that's connected to a Raspberry Pi, so it's nice to still be using it for computer applications!
Ian