Hi all, Just a quick question... is there any difference between a "factory unlocked" iPhone and an iPhone that was unlocked by the carrier later (ie. "IMEI unlocked")? I ask because I'm getting ready to sell my phone, an iPhone 4 that I got over 2 years ago and just had AT&T unlock for me. I noticed the listings on ebay that are listed as "Factory Unlocked" sell for a lot more. So, is there a practical difference (or even any way to tell) that it was unlocked after the fact?