What are these extra holes?

[CrossedCannons]

More questions re stocks.

This birch M2 stock came with a Winchester receiver but lacks any markings. Note the holes flanking the screw hole for the buttplate. My Winchester-marked walnut M1 stock has this same pair of extra holes, whereas my Underwood-marked walnut M1 stock does not. All my stocks are from the CMP.

What are these holes for? To hold the wood while the stock was made? Or for an alternate butt plate or recoil pad? Are these holes specific to manufacturer? If so, which have them?

Information

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[imarangemaster]

I believe they are from the jig in the stock making lathe machine. One of the WW2 vids I watched showed stock making and I think it was a three prong gizmo on the butt end.

[BrianQ]

The holes are the for the locating pins on the cutting machine and can be observed on various makes of stocks, i.e., SA, Marlin, WRA, etc. With size and spacing differing between the manufacturers.

[CrossedCannons]

Thanks Brian (and imarangemaster). That's kind of what I figured, but how were the ones without the extra holes made? My P-U doesn't have them.