The front barrel band is supposed to be welded and pinned. You can see the pin mark on the barrel at least. I don't know what to make of the stock. Some arsenals started using earlier rejected stocks but Nagoya isn't mentioned as one of them. This type front band started with series 7. In fact everything with a late series 7 seems to match your rifle. The series 8 started with the single hole rear sling swivel which yours does not have. the separate fore stock also started with series 8.

I'm betting you have a late series 7. The front sights without guards is also series 7. Mine has them as a series 8 because some in the middle of the run had them.

It is good that you have the pinned front band as it will hold the fore stock in place with the "duffle" cut.