many years ago we wired an art studio that had over three hundred mr-16 lamps in use. our supplier provided lamps from GE. within the first few weeks many of the narrow beam width lamps failed. well, we called the supplier and he provided us with replacement lamps and we changed them. two weeks later the same thing and many of the lamps were from the newly replaced batch. supplier called the GE rep and he came out and looked at the install and found no problems but copied down the numbers off the lamp boxes -- turns out they had what they called an "infected" batch and replaced(lamps and labor) all the lamps and we had no call backs.. no if these were an off brand????
I was putting in some 500W PAR 64 spot lamps today. The old ones' were marked Sylvania, and the new one's were Phillips. The writing on both were absolutely identical. Same font, same type of printing. The ceramic insulator for the terminals had the exact same mold marks for both brands. I swear it was the exact same lamp with two different company names printed on it. I couldn't' see anything one bit different about either.
I say all that to say this... I bet your MR-16 lamps might well be GE's that are rebranded. Private branding is a big trend among all sorts of manufacturers. They'll sell their product any way they can.