Martin,
GGD offered horse cars for the Santa Fe, PRR and maybe a couple of other roads. Pecos River Brass offered one in Santa Fe colors. One end had full width doors which opened to allow buggies and wagons to be unloaded circus style. I think the PRR had some which looked like horse cars but were used by stage production companies. Some horse cars were built with windows which were later covered as the horses got nervous when a train went by.
John Mateyko in Lansing, ILL
The GGD cars are quite nice. I expect them to be a bit scarce as they were don in brass. There were horse and theater cars. I think multiple roads. Here are a couple of snaps of mine. Both nice end of car door as seen in pro types. I believe Quite accurate. 
Well. I dropped in 4 snaps. They go where they want. 😳
Nice models !!!
TrainBub
