I have owned very many pre 64 Win 70's and handled that many more. We are talking in the hundreds. The number isn't coming off due to wear. I have yet to see a renumbered bolt match the font etc of the win factory. The must have had a super heavy duty industrial engraver, at least twice the thickness of any engraver I have ever seen. The hollow vs solid is not an issue. Come the end of the month they assembled guns to make quota with whatever parts were available. They were just guns. They sold serial #2 for heaven's sake. I am not sure about model 70 #1 whether they sold it or did anything special with it.
