Determine age of iPad from serial number

I have a iPAD that I believe may be the very first version. The model is MB293LL Serial Number is GB***Z39. Is there anyway someone at Apple can tell me how old it is by the Serial Number?

It has iOS 5.1.1.......OK stop laughing!!! It has been in a closet for years and works perfectly. Just wondering if you have any info. you can share. Maybe someday it will be worth lots of $$$!

Thanks,

Anita

[Edited by Moderator]