I don't think we know. We only know for sure it was found on the servers after the other two. The number being lower than the others would make you think it is actually the oldest, but who knows as they have gone backwards in the past.
It is working very well for me. Just minor issues, they are very close to having it right. I think the ICS release for this phone will end the debate is it the phone/software or is it the network. From where I sit it is the phone/software as ICS has made my connect rock solid. I am surprised, I always thought the network was mostly to blame.