The original version was designed for use with gas masks during World War II. It was wire-rimmed with cable temples and a "P3" lens shape. The design was a modification of the shape used by the British military. After WWII, the material was switched from nickel alloy wire to cellulose acetate. Initially gray cellulose acetate was used (Frame, Spectacle, Cellulose Acetate, Gray). This was discontinued in 1968, with remaining stocks issued until exhausted. The replacement frames used black cellulose acetate (Frame, Spectacle, Cellulose Acetate, Black).