I don't believe all 23 AA stocks were checkered(mine is -sn 145xx). I'm looking at a picture of one in my 1940 stoger's catalog and it is uncheckered. I have the original hanging tag and instruction sheet for my rifle and it shows an uncheckered stock in the picture. My guess is that it certainly came both ways since my stock is original and serial numbered to the rifle. The two holes in the top of the reciever are for the no. 10 rear sight(19NRA). per my original parts list and the stoger catalog.