The Type B-1 winter flight jacket and A-1 trouser, of horsehide lined with shearling, were designed in 1931 by Leslie Irvin, who re-used the basic pattern for the famous RAF suit bearing his name. Switlik Parachute was the sole contractor. Almost identical in construction were Types B-2 and A-2, the same designs but lined with either moquette (a silk pile) or wool blanket cloth. Both Switlik and Werber Leather Coat built these garments. The article below is from the Air Corps News Letter, April 8, 1932, when the suits were starting to reach units. It mentions that the moquette-lined suits were being used at the same time as the shearling, and intended for fall and spring flying! Indeed the same drawing numbers, 31-2412 (jacket) and 31-2411 (trousers), apply to both types. In any case, the AAC standardized on B-2/A-2 only, lined in a heavy wool blanketing, no doubt to save on cost. Supposedly these were not as warm as the B-1/A-1, which had tested down to -40°C (-40°F). This must have suggested the return to shearling in the B-3/A-3, adopted in 1935.