I have a number of Colt 30 round magazines. These are highly sought after by collectors. They are Army and late Air Force contract 30 round. Circa 1969 to 1971. Black followers. Marked Colt Firearm Division" w/pony and "5.56 MM" on floorplate.
I got these back in the 90's when Fort Hood was getting rid of old stock.
$100.00 each. You get to choose from the remaining mags.