Instructions
Determine what material the train is made from. Tin was used in earlier toys. Plastic did not become popular until the 1950s.
Determine how the toy operates. A Marx train from the 1920s will be a wind-up tin toy. Friction and battery operated toys were not created until after 1950.
Search the entire surface of the toy. Look for any markings or writing to indicate the toy maker. Most Marx toys are marked with the name Louis Marx.