The UC-9 is a really interesting example of the market distortion caused by the 1986 Hughes Amendment. This is essentially an Uzi converted into a form factor than doesn’t look like a gun when folded up. It was designed (independent of the ARES FMG, incidentally) by one Utah Connor in the early 1980s. Only a few complete guns were made before the registration of transferrable machine guns was closed in 1986, but Connor did make “about one hundred” receivers and register them before that date. The project stagnated for years, with Connor periodically bringing a complete gun to machine gun shoots but not pursuing completion of the remaining guns.
Another man, Michael Shyne, encountered Connor at one of those shoots, and was taken with the idea of completing the guns – but his attempts to buy either one gun or the complete project form Connor were rebuffed. Eventually Connor passed away, and the new owner of what turned out to be 76 remaining registered receivers was happy to sell the whole thing. Shyne proceeded to complete the guns, and they were eventually all sold commercially.
Mechanically, the gun is basically an Uzi. It uses a modified Uzi bolt (the recoil spring is fixed to the front of the gun instead of extending behind the bolt), Uzi style grip, and standard Uzi magazines. However, it folds up in a clean rectangular package. When Connor originally designed it, he included a handle and fake antenna to disguise it as a radio. By the time Shyne made the guns available commercially that sort of things was laughably outdated, and so he suggested that it could be disguised as a laptop battery or external hard drive – which are equally outdated today.