The M14 mine is a small ( diameter) anti-personnel land mine first deployed by the U.S. circa 1955. The M14 mechanism uses a belleville spring to flip a firing pin downwards into a stab detonator when pressure is applied. Once deployed, the M14 is very difficult to detect because it is a minimum metal mine, i.e. most of its components are plastic. Because of this, the design was later modified to ease mine clearance via the addition of a steel washer, glued onto the base of the mine.