Has anyone ever come across the Chatwood Milner combination "blisters" used on UK Forces safes? They are a small, hinged unit which are welded and bolted over the keyhole of a safe and the keyhole cannot be accessed until the manifoil combination lock controlled door has been opened. They add very little security but they do make it obvious if anybody has attempted to open the safe.

I would like to buy a couple. Are they available commercially?