50-foot boxcars built between 1937 and 1953 had double 6-foot sliding doors centered on the car side. Beginning in 1950, they received the large billboard lettering.

The first 40-foot cars to receive the new billboard lettering in 1950 had the large letters located near the door and slightly closer to the top of the car than usual.

By 1953, the lettering was positioned further to the car's ends, a scheme that coul.d be seen on 40-foot cars for decades to come.

Double-door 40-foot cars built in 1937 were later repainted into the billboard lettering scheme.
Combination plug/sliding door cars were built in 1959.

Also built in 1959 were some PS-1 cars with STB loaders. Note that the billboard lettering on these cars and the combination door cars was slightly different than the other cars of the 1950s.

At least one 40-foot STB car from 1959 received a Colormark logo, presumably a test for a boxcar red version of the new red/white color scheme of the early 1960s.