03 Springfield experts, I need your help with an oldie.

Just had an 03 manufactured in 1904 (SN 31xxx) come in the shop. All original, but somebody put a heavy varnish on the stock.

I'm assuming this rifle was rebarreled for .30-06, but where can I find the arsenal marks to confirm this? I see nothing but the original SA rollmark and serial number on the receiver. Is it possible that this one slipped through the cracks and is still a .30-03?