IIRC, Center has current contracts with Uncle Sam. Regardless, they are good magazines. A couple of the details I like about Centers better than other USGI manufacturers - the floorplates are damn tight, and they have extra welds down each spine. IMO, Center magazine bodies are the most rigid and will not pop and creak as easily as others if you hold them and twist. The only bad thing about Centers is I have found them less likely on average to drop free from a given lower than with D&H or Okay. Not MUCH less likely, but enough to be noticeable. I have never had a Center mag fail to function properly, other than a few that would not drop free from all my lowers.
Another detail - don't fret if the ones you get have no markings on the baseplates. That's how they have been rollin' for the last little bit, and if the CAGE code is still stamped on the body they are genuine Center mags. Usually delivered in clear plastic wrappers.