I bought an iphone 3g (came with fw 2.1, unlocked), and the seller said that it was from US and that he had unlocked it with quickpwn. I updated it to fw 2.2 (via itunes shift+restore) and it was still unlocked, and when i used quickpwn, the option to unlock didn't appear. After the jailbreak, i didn't use yellowsn0w and it is still unlocked.
Oh, and i looked in the settings - general - about, and there it showed that the model is MB496T, which is said to be from Italy here.
The model + the staying unlocked when i updated is telling me that my iphone is factory unlocked. Is this right? If it is, i'll update to fw 2.2.1 =)
EDIT: is there any way I can be 100% sure that it is factory unlocked BEFORE i upgrade to 2.2.1?