What does SSAA mean on the stock?

[Dan Wilson]

Well if everything else on the rifle you can find is marked E and only the cocking piece is marked W then no, most likely that's not a rebuild. Most likely replaced by a unit armorer or someone as a very small spot repair.
Just because it has a depot/rebuilt facility stamp doesn't mean its rebuilt, if it goes and its in good shape it just gets the stock stamp and put back into WRM stock.

Dan