This is what I think happened.And they seem to have disappeared as quickly as they appeared. I'm guessing this was a one-time run. This might be because when these mags came out, Poly 80 was starting to come under fire from all angles - so they probably stopped doing stuff that wasn't supportive of their core business functions because they needed all the money and staff power they could divert in order to begin to deal with all of the legal, legislative and other bullish!t that was coming their way.
Its too bad as IMO their frames were good quality, ive built a couple serialised and they are very reliable guns.