A possible source of the rifle is one of the many gunsmithing schools, I don't remember any of the students marking the caliber on the rifles they built. Though they generally had pretty plain uncheckered stocks that the students built as part of their training.
At Co School of Trades we were required to stamp the barrel. I've stamped every one since, except my latest M98 with a 27 inch heavy bbl. My stamps are 600 miles away at the moment. I'll get to it....
