B&O M-15a Boxcar
The M-15, a steel-framed, double-sheathed 40' car, was by far the most numerous class of boxcar on the Baltimore & Ohio throughout the 1920s and 30s, with over 11,000 cars among seven subclasses. The M-15a series, 193000-196505 comprised the largest individual group of cars, with 3,390 of them built in 1912. The original M-15 and M-15a were "door-and-a-half" automobile boxcars, so named because they had a second, smaller door next to the main door on each side, permitting a larger opening. The image below is of a Westerfield HO model of the M-15a.