Brian spotted this. I don’t know enough about these to know if this is a prototype or not.
“1950? Prototype Willys – M274 Army Mule
Rolling chassis,
4 tires, both axles,
no engine.
Purchased by previous owner’s father
at Kaiser-Willys factory auction (Toledo OH)
Around 1960
(Kaiser bought Willys in 1953,
AMC bought Kaiser in 1970).
Price: $650
Information Email: jonharknes@yahoo.com“
http://americandreamcars.com/1950prototypewillysm274armymule.htm