It's called a "beta c-mag", and yes it holds 100 rounds. Come to my gunshop and I will order one for you...
Click here to go to see one.
Pricey, and my margin is thin, but if you really want one, I can get them for you...
KCI of Korea has an (apparently licensed) polymer clone of the Beta C called simply the Beta that retails out for half of what a Beta C does.
"Gee, where can I git' me one of them "100 round mags?"
Thanks all for the replies
Guess since I only own an old .30-.30 lever action; 12 gauge pump and a Glock .40, I've been out of touch and didn't realize there were such high capacity mags available (or legal).
Looks like I'm going to have to check into upgrading my "arsenal" as I can see the benefit of owning something like that, the way things are going.