A pretty nice rifle, finding a bolt matcher that is property marked is pretty difficult, not sure I have seen a factory bolt in a property marked 98a... so, not unusual at all, even a period replaced bolt matcher is pretty darn difficult.
Regarding the stock, does it have the take down? Most do by the u-block, but there are exceptions in the t-block and even after the u-block. While Erfurt trends are more numerous than all the other makers (Erfurt made a vast number of carbines, far more than any other rifle producer...), it is amazing how few really nice 1917's exist. The upper end survival rate is dismal compared to numbers made, of those that are anywhere original (German original) more than half show interwar service. Really, when you consider numbers made, surviving trends, it is clear the Germans destroyed massive numbers from wartime Erfurt production after the war... so in a sense the vast numbers made during the war (numbers not matched until Mauser surpassed them in 1942..) are not reflective of relative rarity today, - while huge numbers were made, equally high numbers were destroyed and Erfurt wartime carbines are not especially more common than other large G98 makers, there are vast gaps in trends where several blocks are practically devoid of reports... for instance G-L blocks only possess 11 rifle recordings, none from the k-block... then later in 1917, the dual suffixes, you can have some blocks with a dozen or more recordings!
Anyway, a nice rifle that shows very little later tampering, many that have a property mark show considerable work, often police service with corresponding heavy reworking.