These are marked CAVENEY INVENTION CO. OAKLAND, CAL. FEB. 8,10. and are commonly referred to as Caventy bottlenecks. The lock is interesting. An inside threaded key is screwed down into the lock until it catches. Turning CW one click frees the swing arm allowing removal. Turning one more click engages the ratchet mechanism allowing adjustment on the wearer. Turning one more click activates the double lock which locks the swing arm in place. They are light but secure. These have a nice brown, old appearance but were once plated.