Circa 1918-1928 - There really are no distinct characteristics to these cars so we really can't be much more precise than this. 

Circa 1918-1928 - Lehigh Valley

Circa 1922 - We know this one is from 1922 as it came in a 1922 only set, o/w it's the same as the rest.

Atlantic Coast Line - Note that this car has a definite 'halo lettering' effect which probably makes it 1923 or later. 

Circa 1923-1927, Santa Fe box with halo effect.

This example has a red roof and may be later Circa 1926-1928, but we're not sure of that.