Casterpollox wins the prize!!!!
I don't know the history of the magazine, but I did buy it with the hope it would work in my DCRA .308. It does, actually. I notice, though, that the little screw that is supposed to catch the rim of the spent casing as it is drawn back and force it out, isn't sticking out into the runway quite far enough. .308, or 7.62x51 NATO rounds load into the mag quite nicely and feed into the chamber alright. I will have to have a better look and see if something can be done.
I bought the mag from a fellow at a shoot at Hipwell's some years ago. I didn't know that it would work, but was certainly willing to give it a whirl, as I was having to single load the thing before that.