One of the funniest models I remember was the Gem Camel. This engine had something I had never seen before. TWO backheads on the same boiler. Seems the builder figured if there was a cab, there was a backhead inside. So, naturally, there was no boiler running through the cab. Never did quite figure out what the fireman who stood at the back of the engine did or how they got coal to the "foreward" backhead.
Must have been a fun trip up the running board from the tender with a full scoop of coal.