I read about the Eagle Alpha mags (held 19 rounds) for Sigs, S&Ws, and Beretta/Taurus pistols in 1995, but could not get in touch with them. They had moved or something, and all that I had was the phone number. I got lucky when a friend of mine had a magazine with their mailing address. I mailed them and received an address and business card of a man that supposedly bought up their stock of magazines.
I called him and he had them, but they were in storage (guy sold sporting goods) and to try later. I guess I tried contacting him too late, because I got a disconnected phone number notice with no available number.
The only other information I had gotten on the magazine was that it was constructed like a Ram Line mag (used a constant force spring), and that one owner of an Eagle mag had a rivet or pin break (he did not indicate where on or in the mag) after a time and it stopped functioning. While I am cautious of the mags because of a lack of information, I ordered a couple last week myself for my Sig.