The Model number (and therefore serial) has a slightly different prefix if it has been swapped/serviced by Apple. Could this help provide an explanation in your case? (Admittedly, this may also put the user off, if he thinks he’s gotten “a refurb”, though he’s buying second hand, so...)
Equally. I’ve lost count the amount of times I’ve seen boxes that do not match actual phone. Especially if they’ve come from CeX or the likes. To them, a box is a box is a box! (Which is how it should be really, the box has no function in the scheme of things.)
If I notice a mismatch during sale/taking of photos, I’ll often Stanley knife the serial bit from the sticker on the case
Which is overkill, but at least it’s as pictured”.
Finding the model number of your iPhone is easy. Tap on Settings > General > About and scroll down to the Model section. This setting will show you the nine-digit model number that you can use to determine the origin of your iPhone.
- M – your iPhone is new
- F– your iPhone is refurbished (refurbished by Apple or a carrier)
- N – your iPhone is an Apple replacement phone
- P – your iPhone was personalized with engraving
On newer iPhones such as the iPhone 8 and higher, the model number is also visible in the SIM tray slot. You will need to remove the SIM tray and look.