These were commonly called 'Daley Bottlenecks' because of their peculiar shape. The key is a tiny fork which needs to be inserted part way into the keyway, then twisted 90 degrees and inserted further before being able to turn another 90 degrees in order to unlock the cuff. The bow has notches in BOTH sides which are engaged by the locking mechanism. These differ from the Marlin-Daley Handcuffs by the swivel link between the two cuffs rather than just three rings. These cuffs were used by the Canadian RCMP for many years.