Sometimes hints are left behind to positively date a vintage piece ...like the expiration date on a battery ...best used by May 1938!
Set of early Walthers cars ...brass sides and vestibule ends, bronze cast ends , aluminum sill castings , fiber window sash inserts ....all these would be changed ( cheapened) by 1939 to bring the cost down on the cars .
So set of cars 1936-37 ..battery box under observation car for drum head light ..,remove old battery ..add some DC ..the 20th Century will be pulling out of the station again soon .
Cheers Carey