Yes, the Gilbert AF cars are based on a real prototype which, according to one source, began delivery to the NHRR in 1935. Gilbert first began making them in 1939 in sheet steel for 0 Gauge 3-rail operation. After WWII, Gilbert re-tooled and made the same prototype with more detailed bodies molded from Bakelite (at first), then liquid plastic. Both the pre- and postwar "3/16-inch scale" cars are made to 1/64 scale height and width, but are shortened to about 55 scale feet to enable them to negotiate 19 inch radius curves.
The prewar sheet metal cars came in two different colors of green, plus red, tuscan, dark gray metallic and dark blue (for the Royal Blue sets). Generally, the postwar cars were made bright red, dark red or green, either painted (over gray, cream, or black plastic), or molded in red or green plastic. A few were painted yellow (or molded in yellow plastic) for American Flyer Circus sets. There were also red circus cars which are HTF. They differ from the normal red cars by having yellow lettering and window frame tamping, "AMERICA FLYER CIRCUS" lettering over the windows, plus big "World's Greatest Show!!" tamps on the sides.
Why so many colors? To
sell more, of course!
Later on, some Hew Havens were chromed or painted silver for Silver Bullet sets. Sadly, dark blue S Gauge cars for the postwar Royal Blue locomotives were never offered. If you ever see any, they are repaints.
The S Gauge cars can be found with frames of plastic (often warped), stamped steel (the most common), or diecast metal. There are lit and unlit versions. These cars may come with link or knuckle couplers.
That's about all I can say off the top of my head.
