I have heard the same as Chuck and Ken.
Additions and Betterments are one line on my railroads AFE's. Depreciation is another. Salvage is another.
A fellow researcher, Hudson Leighton used to joke that, the shop would have an overhead crane pull the carbody off a set of trucks and then set a new body on the trucks and stencil the former cars number on the shell and out it would roll. Same old car..... as far as the railroad was concerned.
Jim Dick - Roseville, MN