What a great find. Go follow the link above for the rest of the discussion.
I recently purchased the Hiatt grip shown below. Both the cuff and the key are marked with the name Hiatt and a number "2". The grip is built differently than the standard Hiatt grips that close with a simple catch. On this one the two halfs of the grip come together is a very tight complentary "claw" closure. To open it a screw key has to be screwed in depressing the bottom claw. The grip then pops open. Everything is very tight and the grip is actually very difficult to close.
Once closed it is very secure and there is no way you are going to open it by hand. The spring action is simply to strong.
Overall it is a very interesting cuff for the collection, but it is easy to see why they were never popular. It is just to hard to operate. And to use it you would have to carry it in an open position. - Handcuffs.org Forum