 DATE: The handcuffs worn by Jack were made from stainless steel  which was not invented until 1913. In the early 1900s, handcuffs  were made from mild steel (often galvanized to prevent rusting). The  metallic luster from Jacks handcuffs shows that it was either made  from silver (which was not used on handcuffs in 1912) or stainless  steel.