The NSN is the same for all US GI 30 round magazines.
Plugging the contract number into Google brings up a Marine Corps bulletin on product quality deficiency reports that uses that contract number in a PQR on Cooper magazines.
The sample PQR may not be 100% accurate, but all Cooper magazines were pulled from service due to problems.
There should be a CAGEC or manufacturer's code on the floorplate. Cooper's CAGEC was 30389.