CuffLock

The CuffLock is a regular padlock that uses a handcuff key. In point of fact, this one is rather easy to pick. However, the fact that a handcuff key opens it means one less key to carry.

It would, one assumes, be typically used on a Blue-Box assembly or perhaps to lock a Belly-Chain around a waist. In both cases, the wearer has no easy access and the ease of picking isn't as much of an issue.