IPhone 3GS :: Ways To Avoid Scams

I though I would create a thread for those who buy iPhones via craigslist, eBay, or HoFo They are a few ways to verify what version and if it can be unlocked. Please add if you find anything incorrect or have one of you own.
1. iPhone 3GS are the only models that have Voice Control. Verify this by holding down the home phone to activate it.
2. Know the Apple's website to verify the serial #. This will tell you what version it is. Have the link saved in your pc or smartphone. Calling Apple will take too long
3. As of this post, 3.1.2 and 5.11.07 can be unlocked. modem firmware 5.12.01 cannot at this time. 3.1.3 can be downgraded to 3.1.2, but not the Modem Firmware to 5.11.07. If it really could be done, someone would be doing it and charging alot of $$ to do it.
4. Not sure if this is the case with the new jailbreak, but 3GS model with the 3rd to 5th serial number at or above 940 are mostly likely the tethered jailbreak type. This have been the case from my experiences
5. Verify the size of the phone by going to Settings, General, About. There are times where the back has been changed to represent a different size.
6. Look at the LCD in the light. If you see horizontal lines, the screen may have been replaced. Also replacements don't get as bright as the original LCDs. In my area there are plenty of ads and more stores opening that repair iphones
7. If the buyer is claiming that the phone is unlockable, but it's on the connect to ITunes screen, chances are it's not.
8. Dual Sim iPhones and Mini iPhone are not legit
9. Verify no water damage has occurred by looking at the indicators in the headphone and USB Port.