This is an important item in BeebMaster Econet history, because when in 2001 or 2002 ish, I was forming my first Econet, I didn't have an Econet lead, or any cable, so I cut the wire off this mouse, stripped each end, and soldered lengths of severed paper clip to the wires, which I could then poke into an Econet socket. I found the mouse in July 2015 when I was looking for my PINE manual. The mock-up Econet lead is still lost in library.