A Quick Guide to ATSF Paint
A.T.&S.F. - until 1938
A.T.S.F. - 1938 - 1943
ATSF - 1944 - end
As a very general rule, in the 30s and 40s cars would need repainting about every 10 years. Stock cars, with their hard cleaning, may have shown their wear more rapidly. I would expect very few A.T.&S.F. painted cars to last into the 50s. A.T.S.F. painted cars would have lasted into the early 50s, but most cars by the mid 50s would have been ATSF.
Other immediate give-aways on paint are:
Scotchlite reflective circles - 1958
ACI Labels (the color coded car ids) - 1969
Reweight Dates: in the 30s and 40s all cars had to be reweighted every 30 months.
Maps on cars:
Curved line maps (2 versions) -1940
Straight line map -1940-1947
Ship and Travel - 1947-1958
K brakes were used in the early 1900s. They could not be used in interchange with other railroads after August, 1953. However, most were gone with post WWII modernization.
AB brakes began showing up in interchange service as experimental at the end of 1932 and were required on all new cars built after September 1, 1933.