Austrian Dollar Sign Handcuff

Here is a very rare and interesting design. The Austrian Dollar Sign Handcuff was created in Vienna, Austria by August Froehlich, an entrepreneur in the metalworking field. August was a precision engineer who focused on high security lock mechanisms and rigid or semi rigid restraint designs. I find mention of other designs but can't find particulars. 

These sold for $723.99 after 9 bids. 
 

Below, close up detail of the unique mechanism and keyway.

Above, reverse view in unlocked position.