Checkering and a gold (brass?) insert on the front sight argue for it being a replacement, but.....
I don't have a Gew98 to look at (and can't find a pic right now) but the 96 Swede and my 98Ks front sight blades all have a triangular shape.
The stock on your gun doesn't match the pic emcom5 supplied, but that in itself means little.
Look closely for importer markings, usually on the barrel, near the muzzle. It is quite likely it doesn't have any. Importer name & address were required by the GCA 1968, so if its not marked, it could have come into the country any time after the end of WW I.
I could have been restocked with a different stock (finger grooves) before being sporterized. It could have been rebarreled, with a shorter military profile barrel or it could have had the original barrel shortened.
My 98k has the barrel numbered to the action. My Swede has the bolt shroud and bolt stop numbered to the action. Don't know if the barrel is, its under the wood.
Not sure what is proper for a Gew98. If the number are there, and match then those parts would be original. Otherwise, no way of knowing. Not that it matters in this case, just fyi.
Lots of possibilities all pure speculation. The rifle could have come to the states after WW I and been sporterized any time afterwards up through the 1960s or even 70s. It could have stayed in Germany and served through WWII, either in original shape, or reworked, been brought back by a GI and later sporterized. It could have been imported commercially before 1968. Lots of possibilities, no way to find out really.
It is never a bad idea to have the headspace checked on any of these old guns. Take a good look at any fired brass you have. It is quite possible for a rifle to have excess headspace, even if the previous owner shot it every month for the past 30 years with not a single problem. Unless you get it checked, all you can know for certain is that it isn't dangerous..YET. And you won't know if its going to be, until something goes badly wrong. Which could be 5,000 rounds from now, or it could be the next time you pull the trigger.
It looks like a sweet gun. Its likely fine. Get it checked, and you will KNOW.
The metal in these old guns isn't as good as it was just a few years later. Heat treating was done by eye, and results depended on the qualities of the steel alloy and the skill of the craftsman. Mauser made good rifles, but everybody has an off day. And what was good enough to pass the proof tests nearly 100 years ago might have changed since.