Mercator K55K Knives

The Mercator K55K is of very simple construction: The handle consists of a folded piece of sheet metal, usually painted black, engraved with the outline of a leaping cat and the legend "K55K", with the second "K" being backwards. The blade has a nail-nick by which it may be grasped to pull it open, and it locks in the open position (a lockback knife), after which it may only be closed by depressing a lever at the back of the knife. As of 2013, the knife can be purchased with a stainless steel or carbon steel blade.[2]

The Mercator's construction is similar to that of the French Douk-Douk knife, in terms of the simple folded-metal handle. However, the Douk-Douk is a slipjoint knife, whereas the K55K is a lockback knife and has a different blade geometry.