Circa 1929-1930 - Any 4 wheel boxcar from 1929 and 1939 should have a red roof and an operating door. The colors of the litho also changed in the last couple years but it is difficult to describe unless you're looking at both. All cars on this page have similar characteristics.

The Chicago and Northwestern Ry above is all original, note the halo effect on the lettering where the example below is one that someone took the body off an 8 wheel car and put it on this 4 wheel frame. Why? well the 4 wheel versions of these cars are rarer.

Here's a 4 wheel version of a car with two different heralds, as this picture shows this car is marked N.Y.N.H. & H. on one side and ERIE on the other.

CB&Q Refer from 1929-1930 with door and red roof

Santa Fe box car from 1929 to 1930