Hesalite: I don't know what the odds of finding a "3" bolt head on a virtually unused No. 4 would be but I wouldn't think it would be high. On the other hand, a former owner/ tinkerer might have put a "3" on it to tighten up headspace to the lower limits and for no real reason. I have a Longbranch with a really big "3" on it that was set up by a target shooter to just barely allow the bolt to close on thicker rimmed brass. Gauging it showed I could easily get acceptable headspace with a normal "1" or "2" bolt head. Getting back to your rifle, the only thing I see in the photos that I wonder about is the strap at the rear of the forend. To me that doesn't look like the way they came from the factory. Is the forend Savage stamped?
Ridolpho
Not sure what you mean by strap at rear of forend.