I have a DEC OVMS keyboard for sale or trade. This is used with a PC and a (good) term program to connect to DEC/Compaq/HP VMS systems. If you run the right software it will use all the correct mapping for the many special keys on the board, and I've found some people have created X key modmaps for Linux for these.
MODEL NO.: LK450-AA
REV. NO.: A06
FCC ID: A09-LK450
I'll take offers to buy it, or offers to trade for various Mac/PC computer hardware. PM me to discuss.