The first production Keystone LB-7 (28-388) was converted to XLB-12 at Wright Field in June 1929. The convertion consisted of the replacement of the Pratt and Whitney R-1690-3 radials by a pair of direct drive 575 hp Pratt & Whitney R-1860-1 radial engines.
The XLB-12 was used strictly as a test aircraft and was never intended to be pre-production prototype. Only one was built. The aircraft was wrecked two months after the conversion.
Specification of the Keystone LB-12:
Two 575 hp Pratt & Whitney R-1860-1 air-cooled radial engines. Maximum speed 116 mph at sea level Weight: 13,050 pounds gross. Wingspan 75 feet, length 49 feet 3 inches, height 15 feet 6 inches, wing area 1148 square feet. Two Lewis machine guns in an open gunner's position in the nose, two Lewis machine guns in an open dorsal gunner's position, one Lewis gun firing downward through an opening in the lower fuselage.