Transition era using mostly post war but there is a smattering of latter offerings from the 80's and 90's that fit that era. Most is 40's - 50's Lionel some late 40's Marx with some mid 50's AHM Casey Jones and Indiana Harbor Belt 080 electrially modified for 3 rail they actually do fairly well. Some of the newer stuff includes Williams O FA/FB Alco's and Lionel's O27 1990s Northern Pacific passenger set. While the scenery remians the same there is a definite change between running O27 and O. To my eye they are enough different in size that they usually if not always never share the stage. Marx has a similar problem being more S in scale while O27 in gauge they don't dimensionally flow well with Lionel or Williams in O27 or O gauge. Some period correct O gauge/scale cars from AHM, Atlas, and Weaver including a Gorre and Daphetid box car somthing John Allen would have never run on his HO layout.
Bogie