i had a vaxstation 3100 with that type of connector (15 pins,) and
came with another cable where you could plug at the other end any MMJ
keyboard (and a 10 pins round plug mouse, but in your case, you plug
directly the mouse to the box,) the monitor (on mine) was a 15 pin
like the other two, "male," the cable (15 pins female) has only 3 bnc
connectors, when you find a cable select on the monitor sync on green,
and plug the three in the R, G, and B, and ignore the rest
has been a long time ago ... hope it helps ...