Chris,
While it may have been termed an "Ordnance Wagon" by those utilizing it as such there were no specific "Ordnance Wagons" produced for that specific use. The wagon used was the Model 1855 six Mule Army Wagon. It was (per the contract) painted with a light blue body or box and red (iron oxide) running gear (wheels and under carriage).

I constructed one full scale back in 92 and the Park Service has it now. I'll attach a coupe of pictures of it
Karl F.