thanks for that insight into the B&O caboose... so, WWI ... i suppose that could be a sorta "panic", no?
here is an ad excerpt from Chicago based, N.Shure Co., with the tag line of "World's Largest Novelty House". from the Flyer Champion line and headed up by a Type VII electric locomotive, The Conquerer...
unfortunately i've heard a rumor that the formula for the "NONBREAKABLE HEADLIGHT" has been lost ... 
so i'll take a stab at it, but i believe the Champion line was created as a bridge to transition the less expensive Hummer and Empire Express sets of the 20's and early 30's into this very small American Flyer niche. these 5" cars started to appear in 1932 and were last seen only 4-5 years later.
the set shown is one of the earlier versions including cars with sliding doors, a caboose with cupola and separate riveted couplers. as this line matured, the cars were modified to lower production costs.
operating doors were replaced with simple openings and couplers were changed from separate pieces to formed extensions of the frame...
and the caboose lost it's separate cupola piece.
a sand car was the only other 5" car in the Champion line.
the only variation i've seen is the door colors.
not a set as far as i know, but i'm willing to say there was something close to this...
a few of the Type XV clockwork locomotives ran into this time period and there were clockwork Champion sets offered. more than likely one or more of the low end sheet metal locomotives took over this assignment after the first one or two years. if or when i find an ad i'm sure i will be able to modify it to match.
fun stuff...!
cheers...gary
