40th week?

[TANK510]

I keep hearing and reading about the 3gs that if it's built over the 40th week, that it cant be jb or unlocked? How would you know if it's over the 40th week? serial number?

[Cer0]

The 40th week of 2009. The third digit is your year and the 4th and 5ht are the week. Example mine is **928. So mine was built in 2009 on the 28th week. If it was **010 then it was built on the 10th week of 2010.