I ended up calling EVGA. They told me that the cards were exactly the same and that the serial number was kept to distinguish it from the card sold with the motherboard. He said that at one time the # 256-P2-N525-AX was clocked slower because of heating issues. Most of those were recalled the heat sink was changed but the serial number is still around. I must admiot he didn't sound absolutely sure. This morning I had the card removed from my order before I knew all this and it resulted in it snarling my bank account. (It was paid for with a visa debit card). They charged the whole amount and will take awhile to get credited back again. Anyway, in case someone else runs into this problem, here is the info.
BTW, I will probably order the Battlefield combo anyway which has a serial number listed on the manufacturers website, just to be sure. I know it sounds anal, but I get anal over $500 vid cards.
Oh well.
Thanks again.