Austrian $ Handcuffs
These cuffs unlock by PULLING the lock case up (when it is unlocked) from the bow and rotating the bow out. The bow will ratchet in normally (on one side, and reciprocally on the other side) under normal circumstances. To double lock (i.e. to prevent pulling up) move the small lever sticking out of the lock case. Once this is done, only the key will move it back. Aside from this, the cuff has one other feature: a small fastening aperture which locks along with the cuff and can be used to attach to a lead or gang chain.
Note from Mauro S:
The "Austrian $ Handcuffs" model is from ITALY and not from Austria (or Germany), as you (and some other collectors) wrote...
It was used by "Carabinieri Reali" (italian police during the monarchy period) from the end of 1800's to the first years of 1900's for prisoners transportation.
As you can guess having a pair of them, the use is not very "friendly" (removing them from prisoners is very unhandy) and maybe for this reason they were used for a so short time.
Despite all, imho, they are a very nice masterpiece!