Actually, those blanks appear to be the ones that were in Chama last year next to where I was working on the Jordan spreader. They are used to replace wheelsets on the C&TS passenger cars. The trucks under the passenger cars are the Bettendorf-type AC&F trucks from the 6500 series flatcars of which most of the C&TS passenger cars were built on. The Chama shop routinely replaces wheelsets on these trucks as they wear out. You can see the skids of wheels in the foreground of this picture I took last year in May.......
I could be wrong about the location, Dave may have photographed a similar skid of wheels on the D&S since I don't remember seeing PO tickets on the wheels in Chama.