"G" is the black industrial finish. I think Snap-on sometimes provided the industrial finish on items that typically didn't have the option to customers that wanted it if they bought enough quantity. There are GXV wrenches out there that have a similar "after the fact" added "G" to the nomenclature. This seems to me to make even more sense on a ratchet like the GS-71 above where the markings are not roll stamped.