This looks like a large digitizer board (a.k.a. digitizer, digitizing tablet, graphics tablet, and variations) with a map overlaid on it. They were very popular in CAD (computer-aided design) applications in the '80s and early '90s, and are, to my surprise, still available today. They are quite useful for any application which requires precise coordinate entry, such as tracing outlines of objects for machining, or, as shown here, inputting map coordinates.
The board has a fine wire grid inside it, and the cursor or pen creates an electrical field which is sensed by the grid. Depending on the resolution of the grid in the board, it can determine the coordinates of the cursor to a very high degree of accuracy. Modern ones work over USB, but older ones would use some form of serial connection to report the cursor's position.
It can sometimes be hard to find information on these devices, since, without knowing what to search for, your search results will be skewed toward modern graphics tablets and tablet computers.
More information is available from The Logic Group's Logic Trace Digitizing System page and their Digitizer Board page. Additional manufacturers' boards boards are shown at DigitizerZone.
(I have no affiliation to these sites; they're just ones I turned up when I searched.)