There may be a post regarding this but I wanted to share the information as this will save many a lot of heartache when looking to jailbreak and UNLOCK the Iphone and wanting to avoid 3.1 at all costs.
If anyone is in the market to buy a new Iphone from Apple or ATT here is a surefire way to make sure you DO NOT get a 3.1 version. Apple is now at a point to where they are pre-installing 3.1 on their phones. After EXTENSIVE research, I actually did this yesterday and it was awesome.
The serial numbers on an Iphone 3g and 3GS are defined as follows.
The 1st 2 number are the location that the phone was built
the 3rd number is the year it was built
the 4th and 5th number is the week of the year
Soooooo, here is the key. The 3.1 was released on Sept 9th. That is the 37th week of 2009. Bobbi Church and I went into an ATT store, told them specifically what we wanted which was a phone that had the following first 5 numbers. XX936 ----(or any thing LOWER that 37). He came out, it was XX936- we opened it up and VIOLA !!!!! 3.0.1 Version on the phone. Needless to say we were joyous
Here is the best part of the story. Our 1st stop was an Apple store. We went into Apple and talked to one of the reps. He actually said that he had NO IDEA about what we were talking about and that Apple has never educated any of their staff on the above info about serial numbers. (WTF) ? I actually kinda got the impression that he thought we were nuts. Well, the Apple store didnt have any 3GS that fell under any of the above parameters so we carried on to the ATT store. The same thing happened at the ATT store. They had no concept of what we were talking about and you could see the manger standing to the side listening with a, (these people are idiots) look on his face.
Truth be told. The above is true and it works. Walked out with a 32gb 3GS, 3.0.1 version, soon to be unlocked and jailbroken.
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UPDATE TO THE ABOVE IN MY POSTING
Please read the post from decagon that is on this. Looks like what I said wasnt failsafe. There is still hope if you can go back as far as you can in the weeks of the serial numbers.