During my daily perusal of onsite auction/sale offerings, I found this 1900AE
http://gastatic.com/UserImages/172/9...wm_4377778.jpg with a similar hole at the bottom of the rear grip strap to the hole in the '06AE I bought last year. I presume this one is tapped, as well; mine arrived with a knurl headed thumb screw installed in the hole.
I believe these holes were drilled and tapped, retrofitting the pistols to hold a shoulder stock. We have seen board stock, and Ideal shoulder stocks, but I've not encountered a pic or description for this particular design concept for attaching a shoulder stock. Anyone know what one of these might have looked like?
D.P.