All conjecture, but the rifle could have been a NM rifle, but not sold through the DCM. I don't know how they got out, but there are NM rifles out there that were not sold through the DCM. It could have been returned to SA in the time frame of the barrel date to have a new NM barrel fitted, getting the SA/SPG stamp on the original stock at that time. If it had been a complete rebuild, the stock would have been changed.