I have both marked magazines on hand and they are exactly the same magazine in fit/finish right down to the position of the spot welds on the spine, 'cept the roll marks and the base plates markings.
The NHMTG Hartford AR mags have the same cage code as the Okay Ind. mags. The cage code for both is 33710.
Okay Ind. is the present contract for Colt mags. The magazines manufactured for Colt are stamped with NHMTG HARTFORD, CT, the cage code, mfg date and Leo markings.
The Okay stamped mags are only marked with the Okay logo Industries Inc., cage code and mfg date, but without the Leo stamping on the opposite side of the mags.
Here's a link to the Business Identification Number Reference System.
http://www.bpn.gov/bincs/choose.asp
Hope to have clarified this for some.