Seen one of these here in England, all original, except mis-matched bolt for about US $300.

Has the typical Nazi Proof Marks and on top of receiver "1937" and the Portuguese Crest.

Side of action the "Mauser Werke Etc., etc." roll stamp.

Now I know that these are good to use as a base for a custom rifle AND make some money back by selling the woodwork...but does it have an intrinsic value as it has that mis-match bolt?
Now I know that

Those ate rare even with the mismatch bolt which might just be a K98 not a Portguese. I would leave it as is.