It looks like an FN rifle to me. Most new haven rifles have blued extractors and a folding rear sight. Also if you unscrew the cocking piece assembly, a new haven rifle will have coarse square shouldered threads, FN rifles will have fine tapered threads.
I’m guessing it’s a South Carolina FN.
This is what I think too. Post New Haven, pre-Portugal, so, an SC FN. . My late New Haven 375 had a stainless extractor and ERA rear sight, which is what this one looks like.