I believe the difference was the gear/wheels used on the Preiser Barnes Wagon compared to the gear/wheels on the Preiser Golmer Mirror Wagon; they were both a little different. They fetch a premium when you can find them. Some of the Walthers resin kits came with these Preiser produced under gear sets instead of the Wiking produced standard under gear with pneumatic tires included with most of the wagons.You may have noticed a couple of numbers were skipped in the Great Circus Train Accessories series, I have no info what so ever about those 3 numbers.
You may also have noticed I skipped numbers 1390 and 1391 in the GCT wagon series, those two kits were a Barnes chassis and a Gollmar chassis to finish your wagons in a different time period. The main difference was wooden parade wheels or rubber wheels, I think.
Great info on the accessories. I never realized there were so many.