Knuckleduster model SKULL BLACK.
By the late 19th century, knuckledusters were incorporated into various kinds of pistols such as the Apache revolver used by criminals in France in the late 19th to early 20th centuries. During World War I the US Army issued two different knuckle knives, the US model 1917 and US model 1918 Mark I trench knives. Knuckles and knuckle knives were also being made in England at the time and purchased privately by British soldiers. By World War II, knuckles and knuckle knives were quite popular with both American and British soldiers. The Model 1918 trench knives were reissued to American paratroopers. British Commandos even had their very own "Death's Head" knuckle knife, featuring a skull-shaped brass knuckle handle.
A notable knuckle knife still in use is the "Cuchillo de Paracaidista", issued to Argentinian paratroopers. Current-issue models have an emergency blade in the crossguard.