Here is a cool find from earlier this summer. I stumbled on this hybrid-yarder in a semi-remote, or at least overgrown, portion of someone’s property. They had no idea it was there. Admittedly Im not an expert in the manufacture history of logging machinery, but I would consider this the final evolution of a stream donkey. There was a period in the 1950s where tractors, trucks, and smaller better chain saws became widely available. Still old technologies were still used. In this case, a stream donkey design, just replace the boiler engine with a big diesel engine. The plaque on the motor was stamped 1959.
Basically it is a powerful wench. Its sits on the wooden sled and can be dragged through the woods by simply wenching it along. You would find a location on the side of a hill anchor it with cables to nearby trees and stumps and then yard, or wench, up logs from way down the hill. This one must of broke down and was simply left there.