Re: "Reclaimed material"
So long as the railroad had an option of using the material again, it could be set aside as "reclaimed" for accounting purposes.
So, in the beginning when you convert four engines from slide valves to piston, you have 4 sets of slide valve cylinders that could be used for the remaining 11 engines thus they are "reclaimed".
Same goes for tubes, because you could either safe end them or shorten them to use in a smaller locomotive.
When you apply Walshaert gear, the Stephenson gear material becomes "reclaimed" because it can be used on other engines with Stephenson gear.
This all works until you get done with rebuilding the class entirely and then things like the cylinders have "no future utility" and thus cannot be classified as "reclaimed".
The basic idea is that the managers and the bean counters want both low costs and a quick pay out on upgrades done. So if the upgrade costs less on paper, the managers and the bean counters are happy, and they guys in the shop look good, never mind if the stuff sits outside in the weather for the next two decades until it finally becomes "scrap" because at that point all of the people that did the work are somewhere else or just gone, including the managers and the bean counters.