A guy at my local proshop has AM#00709. I may be trading him my minimag for this relic and about $150. The body/barrel design is much different from newer mags, there is actually a breach in this mag...the barrel still has the twist lock pin, but the barrel does not have a hole for the ball to drop into, the barrel does not go back that far. I'll see if I can't get pics of it once I get it. The gun still functions great, and it has one of the older metal gripframes.
Nice find!