I will go out on limb and guess that the receiver was a 98K before Alpine did the machining on the tops. I say that based on the thumb cutout along the left side wall and the evidence of a "stripper clip" or "charger" support ledge. It is a bit of a trick question, because I have military Mauser 98, made by FN, that are identical. I also have "commercial" Mauser 98's, made also by FN, and others, that do not have that thumb cut-out (are solid left side wall) and never did have that charger ledge.
I would be guessing that it makes a difference about trigger, because a military 98 would have a lever safety on the rear of the bolt shroud - you have that former military bolt shroud that has been worked over, and that military safety lever is removed. And, Alpine appears to have installed a trigger with a side safety that required some inletting into your stock, just behind the bolt handle. Any replacement trigger that you get will need a similar side safety, and will likely require some attention to that area to fit and work properly. Some of those, like made by Parker Hale and Santa Barbara, also had a lever inside, that comes up through a slot within that receiver, and would lock the bolt shut when the safety was slid to "SAFE".
Not real certain what you want or need, but that side safety is telling me that Alpine already has installed an "after market trigger" - unless they invented a "cheap" way of creating a trigger blocking safety and using the original military trigger parts. You would have to remove the receiver from the stock to be able to see?? FYI - I am pretty certain that Alpine, was like Parker Hale, Sako and others at that time - using surplus German receivers from WWII that they "sporterized" and installed new barrels, etc. into new made stocks - including drill and tap for scope bases, and altering the bolt handles for scope use - to sell to the public, who wanted inexpensive, very durable and robust hunting rifles.
