These handcuffs are the very earliest Peerless Handcuffs model ever made. They use a solid post key with a single bit. They double lock by turning the key in the opposite direction of unlocking one full revolution. To double-unlock turn the key in the unlocking direction a full revolution before single-unlocking. The two cuffs are connected by a single elongated link. The bows have grooves in them to prevent picking. Still, the cuffs are relatively easily shimmed if not double-locked.