At one time these extremely rare cuffs are said to come from Russia or Germany. The quality of workmenship implies the latter is likelier. It is now beleived that they were made by prisoners at the Kakola prison in Åbo, Finland. They were most likely made sometime in the late 1800's to early 1900's. They are called "Schwartiger" by some collectors.
VERY heavy and chunky, with these on it is very clear that you are going nowhere soon. The lock is rather stiff and uses a simple barrel key with an extended nib, not unlike the one used in Mattatuck cuffs. The cuffs are adjustable but not double-locking. They fit average wrists rather snugly.