Yep, it's a tunnel washer. Or was.
I bought it, for cheap, as it had the working gears (2,000:1), front and rear PTOs and hydraulics. The washing apparatus itself is a lot like a backhoe, except that it has a break-away feature halfway on the dipper.
Thought about swapping the brush for a flail mower to use along the ditches. That wouldn't have worked out well since it would've been a two person job, and the hydraulics for it are operated by switches instead of levers.
Would've been great for keeping a solar farm clean, but we don't have any around here.
Removed the tunnel washer stuff, was then offered more than twice what I had paid for the Unimog, mostly for the working gear equipped transmission. So, if somebody wants a free tunnel washer setup, come and get it.
Although, I'd like the keep the 800 something lb. ballast weight that could be moved laterally to help compensate for the sideloads. And notice that the rear suspension can be locked out.