FWIW, the book Southern Pacific Ten-Coupled Locomotives by Robert J. Church has a chapter set aside for this one. Some pictures of the boiler construction and of the locomotive at Baldwin. Probably not worth while buying the book just for that but if you could get it thru the library. Me, I collect books. Santa Fe Locomotive Development by Larry Brasher also has a couple pages about testing the locomotive. This was the 1st information I had ever encountered about the locomotive.
Mark