The Hamburg Eight are made of nickel plated brass. 

When folded (only in one direction) the cuff mechanism allows the cuffs to be opened.

When fully extended, the bows, when pressed down, will lock.

To unlock the cuff a key needs to be inserted into the lock case. The key pushes the bolt out of the way and allows the cuffs to open.

Inner diameter top to bottom: 6.2cm
Inner diameter side to side: 5.2cm
Inner circumference: 18.5cm
Weight: 540g