TEPLOPAROVOZ.  Here's a clip from what appears to be an original Soviet documentary illustrating locomotive development during the Stalin era.  It suggests that one of the early diesel locomotives, a boxcab on what looks like the running gear of a Milwaukee bi-polar, made it into preservation.

There's also footage of a test of the Stalinets TP-1 teploparovoz, no. 8000, that might illustrate the uneven power output of the steam and diesel strokes of the opposed pistons.