This rather rare handcuff is a Maltby high security model that take a special flat key. Most Maltby handcuffs have a very simple key as shown at the top or the above picture. Such models can be picked open very easily with almost any metal object such a paper clip. The high security model takes a special warded key shown at the bottom of the above picture. The lock is much more difficult to pick. They are manufactured by the Mattatuck Co. of Waterbury, Conn.