The Maltby

 

This Maltby is on sale for $147.67 with no key. The seller states: "Up for sale is an antique set of Maltby handcuffs made by the Mattatuck Manufacturing Co in Waterbury, CT.

I do not have a key for these handcuffs. One side does not appear to lock. The other side will lock.

The swing arms will stay open when fully opened and the paddles are up. One of the paddles does not have a good spring. 

These will be shipped unlocked, so that you can investigate the inner workings. However, if you don't have a key, I suggest that you close them, unless you have a key and can confirm whether they reliably function or not."

Here you can see the activating lever arm. When the wrist depresses this spring loaded lever, the cuff shackle is rapidly swung into place and locked. 

As the seller wrote, these are manufactured by the Mattatuck Mfg. Co which obviously makes the Mattatuck restraints. You can also see the round keyhole with center pin.

This set is a very good condition example of the Maltby which works exactly as intended with the 1 original key. The seller provides a video showing the activating lever arm snap shut action. The current price is $356 with 15 bids, with just over 4 hours remaining in the auction! Will update with final sale price. 

UPDATE: These sold for $927.56 after 25 bids. The sentiment on the Facebook collectors group seems to be that this seller gets higher prices and more interest in his auctions because he's an amazing and well known escape artist. 

This is the patent diagram showing just how these complex, clockworklike mechanisms function.