(Yaaawwwn) Hey, is it morning already? Why didn't anyone wake me up?
Well, the chuck is NOT a Jacobs #1A, judging from the photo. That's what is on the only 1/4" Black & Decker I have from around that time, with the hexagonal motor section. I think that the holes were for a Tommy bar, and then you turned the outside by hand, using the diamond knurls for grip, but that's only a guess. Can you try doing that?
Oh - and I HAVE been on here since October, though only briefly and sporadically. Had several outdoors jobs that needed doing, and don't want winter to arrive before I get most of them done. Think I may have responded to some items in Whatzit forum.