I had thought this was an earlier vintage on our first visit to the museum, but on our second visit I checked, and the sign says "Rail autocar, Warszawa type, 1968" and refers to "personal transport." Thanks to information from Jarek, it was based on this Russian model http://en.wikipedia.org/wiki/GAZ-M20_Pobeda and was produced in Poland.

This time the sun wasn't working against me (since there was none), and we moved the distracting sign out of the way. Getting a shot of the front of this interesting form of transportation was one of my missions for our return visit to the museum ;-).