In 1947 the Baltimore & Ohio acquired ten 2-6-6-4 simple articulated locomotives from the rapidly dieselizing Seaboard Air Line. No. 7700, shown here in an unprovenanced photo purchased from an eBay vendor, was the Seaboard's No. 2500 of class R-1 and was reassigned to class KB-1 on the B&O. These engines, erected in 1935 by Baldwin Locomotive Works, had cylinder dimensions of 22x30 inches and rolled on 69-inch drivers. They mustered a boiler pressure of 230 p.s.i., weighed 480,000 pounds, and developed 82,280 pounds of tractive effort. Evaporative heating surface totaled 5513 square feet, superheating surface 2397 square feet, and grate area slightly more than 96 square feet. Used in fast freight service by the Seaboard, these relatively high-drivered 2-6-6-4s were not so well suited to the B&O's mountainous gradients and, moreover, suffered leakage from the piping to the front engine unit which the B&O corrected by the installation of ball joints. All members of class KB-1 were removed from the roster by 1953.