Mercator K55K

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.

[2] The Mercator's construction is similar to that of the later appeared French Douk-Douk knife, in terms of the simple folded-metal handle.

The correct code deciphering according to the website of the current manufacturer would be: "K" for "Kaufmann" (the name of the original producer), "55" for "Hochstraße 55" (the address of the original company residence in Solingen, Germany), and the inversed second "K" (for "Katze" which translates to "cat" - the knife's main emblem).

[3] This knife gained popularity in the United States following World War II, as returning servicemen brought Mercator knives home from Germany.

The Mercator knife also found some popularity with delinquent youths, and by the mid-1960s the "K55K" or "K55" was described as the "weapon of choice among the older teenagers of the South Bronx.