Rivolier Convict Leg Irons

Used in the French colonial prisons about 1900. The lock is just a recessed bolt, but it’s surprisingly effective when done up tight. Central ring is probably for a chain-gang chain and / or to enable to leg irons to be locked down to a bunk. These are similar to the Lilly Leg Irons leg irons, the key bolt has a circular+cutout rather than square shape.