The American-made Gellman Sew-Gem is an interesting machine in several ways. Besides the unique chain-drive that Jon mentioned, it is also one of the few machines with a right-hand round bobbin. The bobbin is on the right side of the needle, beneath the front slide plate that is similar to a vibrating shuttle (long bobbin) machine. The larger square end slide plate doesn’t have anything under it. I guess that it was put there to make it look like a regular sewing machine of the day? If you don’t feel like re-wiring it, I think it’s unique enough to just have setting around as a conversation piece. I haven’t seen many of them.
Here’s a photo of my Gellman Sew-Gem 215, serial #R016837.
CD in Oklahoma