Not AC, but is this tractor rare?

The Uni Tractor isn't that rare. I have seen a bid on a few of them. The idea was to have one power plant to run all your implements. You will see most of them with pickers, combines, and balers mounted on them. I haven't seen any with the attachments in these photos and supect them to be only drawing for the r&d department. These Uni's are later gold models since it has a valve in head enigine. The later models MM built are knowen as the brown mules since it is painted the Dana Brown that MM used in the early 60's. MM built these from 1951 to 1963. In 1963 MM sold the UNi system to New Idea.