contractors made the frames and ground the lenses. These included American Optical, Bausch & Lomb, The Chas. Fischer Spring Co., Willson Optical and Rochester Optical Co. Frame and hinge design varied slightly from contractor to contractor. Despite being designed for utility, these glasses had advanced properties: teardrop-shaped and convex lenses, plastic nose pads and a prominent brow bar and featured flexible cable temples. The nickel plated frame was made of a copper based alloy to prevent offsetting compasses. The "teardrop" shape lens of the AN 6531 was designed to accommodate Air Force pilots who were constantly looking down at their instrument panel while in flight, and influenced all future Aviator style lens shapes. The AN6531 Comfort Cable aviator sunglasses frame kept being issued by the U.S. military as No. MIL-G-6250 glasses after World War II with different lenses as Type F-2 (arctic) and Type G-2 aviator sunglasses but fitted with darker lenses until their substitute the Type HGU-4/P aviator sunglasses became available in the late 1950s. After World War II AN6531 Comfort Cable aviator sunglasses were available for civilians on the surplus market. Subsequently, civilian models and options appeared without a frontal brow bar and with plastic earhooks. Since everything military was in fashion in those years, these glasses became popular among the people and companies got their bearings on time and began to promote such glasses for civilian use in the 1940s and 1950s. Commercial history Bausch & Lomb In 1929, US Army Air Corps Colonel John A. Macready worked with Bausch & Lomb, a Rochester, New York-based medical equipment manufacturer, to create aviation sunglasses that would reduce the distraction for pilots caused by the intense blue and white hues of the sky. Specifically, MacCready was concerned about how pilots' goggles would fog up, greatly reducing visibility at high altitude. The prototype, created in 1936 and known as "Anti-Glare", had plastic frames and green lenses that could cut out the glare without obscuring vision. It went on sale to the public in 1937. Impact-resistant lenses were added in 1938. Ray-Ban Aviator The sunglasses were redesigned with a metal frame in 1939 and patented by Bausch & Lomb as the Ray-Ban Aviator. According to the BBC, the glasses used "Kalichrome lenses designed to sharpen details and minimise haze by filtering out blue light, making them ideal for misty conditions." In 1936 Ray-Ban had been founded as a civilian division of