The Martin B-12A was the production version of the YB-12. The A model had an extra fuel tank (365 gallons) installed to increase range, reducing the top speed by a few miles per hour.
In January 1931 the U.S. Army took over the responsibility for coastal defense as a result of the MacArthur-Pratt agreement. This would allow the U.S. Navy to take on a greater role in long-range sea offensive operations. The Navy, like the Army, was very limited in size in the 1920s and early 1930s. With the acquisition of coastal defense duties, the Army converted some B-10 and B-12 aircraft to float planes.
Production version of YB-12
TECHNICAL NOTES: Armament: Three .30-cal. machine guns and 2,260 lbs. of bombs Engine: Two Pratt & Whitney R-1690-11 Hornet radials of 700 hp each Maximum speed: 212 mph Cruising speed: 165 mph Service ceiling: 24,200 ft. Range: 1240 miles maximum with normal bomb load (1,830 miles ferry range) Span: 70 ft. 6 in. Length: 44 ft. 9 in. Height: 15 ft. 5 in. Weight: 12,980 lbs. gross Serial numbers: 33-163 to 33-177 and 33-258 to 33-267