Sorry JD, I get carried away with the abbreviations some times.
NO= National Ordnance.
The major 1903/1903A3 roll marks.
RIA=Rock Island Armory
Don't be concerned about the National Ordnance cast receiver. It's a post war part and well be just fine for shooting. In fact there are current 1903A3 reproduction snipers being produced and sold for about 1K that use a cast receiver I believe.