The rotary itself has wheel sets with long axles as they were is a standard gauge truck frame. The OM did doesn't have that style of wheel though. They are like the OY wheels. I'm sure the wheels were there for weight as Dave said, the tender was run backwards so it was being pushed from that end. The Aux tender for OM had a wooden cover over it in earlier days and seems to have lost it about the time it was painted gray. The Water leg valves are strange on the overland model and I put the normal D&RGW style on mine.