Classified Repairs *LINK* *PIC*

Here is CN's explanation of classified repairs, but the definitions were standard throughout the industry. Note that they don't even call them an overhaul, much less a rebuild. I doubt that any of the K-36's has ever had more than class 3 repairs, which is what #488 is receiving now. When the various C's received their new boilers, that would have been class 1 repairs.
IMHO, the only time a steam engine was rebuilt would have been when its form was substantially altered during the process, such as when the C-41's were rebuilt into the K-37's, or when AT&SF 4-8-4 #3751 was rebuilt from 73" drivers to 80" drivers, and was unrecognizable as the same engine.
If the information is available, it would be interesting to know how much money was spent on #481 during her last “repairs” at Alamosa compared to #497 or #473. That would tell the most about “who got what”.