Japanese Figure Eight

I believe this is a Japanese figure eight handcuff which was found in a private auction with some other Asian artifacts. The key appears to be original and the spring lock works perfectly. There is a small hole in the frame adjacent to the lock which coincides with a hole in the bow when the cuff is closed. I assume this was to allow a wire to provide a kind of double lock for security.

I have seen photos of these cuffs but always wondered about the size which turns out to be about the same as some of the early UK restraints.
Does anyone have one similar?

Damon

You keep finding some amazing stuff. Well done and thanks for sharing.
Paul D