When you are kicking the tires on a used iPhone ($1,149.00 at Walmart), there is no Carfax report you can turn to for the iPhone version of a vehicle history. You can inspect the iPhone for signs of damage, but you can't know if the current owner bought it new just by looking at it. Perhaps the seller is trying to pass off a refurbished or replacement model. Knowing this bit of history about a second-hand iPhone might sway your purchase decision. At the very least, it can help you negotiate a fair price.

Thankfully, there is an easy way to check the status of an iPhone (or an iPad ($291.38 at Amazon.com)) to determine if it's new, refurbished or a replacement model. There's also a fourth category for models that have been personalized with Apple's engraving service.

To check the status of an iPhone, go to Settings > General > About and take a look at the line for Model. More specifically, take a look at the first letter of the Model number. Here's your key:

• M: new
  
• F: refurbished
  
• N: replacement
  
• P: personalized
  

So, if you see a model number like FQCP2LL/A or NLY72LL/A, then you might find yourself with a bit of leverage to negotiate a better price. Or a reason to walk away from the deal.

If you are not a buyer but a seller, then here are the best ways to sell or trade in your iPhone.