Hi Beggar-

The Monte Carlo stock design was adopted in 1951 and first cataloged for Standard Rifles, Featherweights, and Super Grade Rifles in 1952.  So it’s possible to find M70s with 1951 S/Ns that have original MC stocks, since the factory would have wanted to build up some inventory before adding the option to the catalog.  Prior to that any rifle with a factory original MC stock would have to have been special ordered.  While such rifles no doubt exist, the vast majority of pre-1951 M70s with MC stocks these days have had their stock replaced. 

Versions where the MC was not a cataloged option:  Standard rifles (1936-1951); Carbines (1936-1947 – when discontinued); Super Grade rifles (1936-1951); and all rifles using the Marksman stock (National Match/Target Rifle/Bull Gun).  The Featherweight was available with either MC or low comb NRA stock from the outset (1952) until the low comb option was dropped after 1959.

Hope this helps,

Lou