I've always had a bit of a fondness for this one. It's a late-thirties Riedel Imme. In addition to both front and rear suspension with dampers, it had cantilevered front "fork" and swing arm. The single-side swing arm also doubled as the exhaust pipe. Changing a flat tire was SUPER easy. AND the wheels were interchangeable. Some owners carried a whole spare tire/wheel in place of a saddle bag. The engine is mounted to the front portion of the swing arm and moves up and down with it. This eliminates the need for a heavily sprung chain tensioner, as the geometry between engine and rear drive sprocket never changes. All in all, a remarkable, innovative, and attractive little bike which was far ahead of its time.