Hi mrcvs-

Do you have a specific example in mind?  Reason I ask is that for me (speaking personally) the impact on value could be from 0 to 100%, depending on WHY the bolt S/N is missing.  I know that doesn’t help much.

I’m sure you know that the bolt S/N was applied during assembly after final determination of head space and test firing.  By this time all the parts had been polished/blued.  So the only “rough” marks on an original finish M70 are the WP proofs on the barrel/receiver and the etched number on the bolt.  Some reasons why the number might be missing:

1.  It was never applied (unlikely).  Alternatively, it is there but was faint to begin with and might have been worn further from the bolt sliding back and forth over cartridges in the chamber (possible, although there are usually some traces left even if the number is no longer legible).  I have one such rather worn bolt in the parts drawer from a transition M70 numbered somewhere in the 70000’s, where one can barely make out that there was a number at one time.

2.  The bolt body was replaced.  If a replacement bolt was ordered from the factory it would not be numbered, as this was done only after fitting and test firing.  From sometime in the 50’s (I think) Winchester required rifles be returned for new bolts (or barrels).  If a replacement was done at the factory, I’d expect the number to be there, but if done outside it might not be.

3.  The rifle was refinished, specifically the bolt reblued and bolt body polished.  This might completely remove a faint S/N.  In any event it would make what was left of the number very “smooth”, which it should not be given when in the assembly process it was applied.

4.  The rifle is a fake late Super Grade.  This issue here being that on ’55 and later SGs the bolt body was jeweled before the rifle was assembled, hence before the serial number was inscribed.  Anyone coming along later and jeweling the action to replicate a SG is likely to have removed the S/N in the process.  So I’d be very suspicious of a SG with an unnumbered jeweled bolt.

As you might imagine, these things would have different effects on value, so your question is not easy to answer.

Lou