April 15, 2005
Years ago I had a pre64 mdl70 and it had it on the bottom of the bolt pretty much in the middle of it. It looked like it was done with one of those hand engraving machines. I have a newer model 70 now and it has some numbers in a slightly different spot directly under the bolt handle but it is egraved with a hand machine too.
November 5, 2014
The S/N was electropenciled on the underside side of the bolt AFTER the rifle was proofed, so as to identify the correctly headspaced bolt for any given receiver. It should be located near the anti-bind lug, like this (on a 1949 M70 Super Grade):
Like Clarence says, an “electropencil” is a gadget that uses an electric current to mark metal surfaces. Sort of works like a miniature arc welder. It is not a rotary bit graver, like a Dremel tool, for instance.
Sometimes the bolt S/Ns were written hastily and not very deep and get worn off (or partly worn off) during use, but the most common reason for a missing bolt number is a refinishing job where the bolt body was polished (or engine turned) and the number not restored. Since these numbers were added only after the fully finished rifle was proof tested, the number should always be there and it should be “rough” (not polished over) excepting for normal wear.
Hope this helps,
WACA 9519; Studying Pre-64 Model 70 Winchesters
Louis Luttrell said
The S/N was electropenciled on the underside side of the bolt AFTER the rifle was proofed, so as to identify the correctly headspaced bolt for any given receiver.
This was done at Spfd. A. for 1903s chosen to become National Match rifles by trying different bolts in the rcvr. until by random selection one was found that produced the desired headspace, after which it was serialized. My guess would be the procedure for headspacing 70s was the same.