Steam Era Cab Cars?!

The GWR Autocoach.

https://www.youtube.com/watch?v=whp50RnZ5s8

I... didn't know this was a thing. Always figured it was possible but didn't know some madman made it a thing. Brings up the question if anyone tried this method to link 2 locomotives, Smooth power application from both loco's simultaneously while only needing 1 extra fireman (witch if memory serves was the cheaper of the 2 crew anyway) for double the power and some linkage maintenance and no fiddly flexible steam joints like a mallet or garratt type. SOMEONE had to think about it.

I knew that in the steam era, before the bilevels, the Chicago & North Western would practice an extremely crude form of push-pull in suburban service when deadheading back to the city (through the use of air signals and coaches equipped with end windows) but the operation in your video appears to be the real deal.