I've seen pics but none for sale. Did they make up some prototypes that never made production ?

I don't think they ever made any.

Too bad. I think they would have sold great.

I was just looking at my two 40-rounders the other day and wondering if they will ever release a window version. I think when you start to reach higher capacities like that, the window really starts to come in handy (longer time between reloads would make it harder to maintain a sense of your round count). I have a feeling that the 40-rounder isn't all that popular - it's just a little too long and unwieldy. While the D-60 costs as much as six 40-rounders, is heavier, and more complex, I'd honestly rather have one D-60 instead of six 40-rounders because of its compact size and higher capacity. I just wonder if they decided there were more promising things to put effort into rather than producing the windowed PMAG 40.

you make some good points but I think the 40 is in a way a niche magazine for those who are serious competitors in events like 3 gun. where you have prescribed moments to do reloads.