It must have been rebarreled.
The markings indicate it is chambered for 7.62x51 NATO.
The original rifle - as identified by the Old Gun Smith - was chambered in 30-06.
The 7.62x51 round was not designed and adopted (which was for the U. S. M14 rifle) until about 1956 or so.
Therefore, the rifle has been re-done. That is probably (I'm speculating here) when the bolt was turned down; that seems to be a later style fad. The straight out handle is more convenient for fast cycling, but tends to get in the way more when carrying. Straight bolt handles also tends to get in the way of mounting a 'scope.