Exactly how is that screen being reached? It does not appear to be a standard iOS information screen. If you have access to the phone, navigate to Settings / General / About and scroll down, where you will find the Model #, Serial #, various MAC addresses, the IMEI and the ICCID, as registered in the firmware and hardware of the device. Make sure the Serial # listed there corresponds to that imprinted on the back of the phone.
Also, IF you do go thru the sale, MAKE SURE the device is released from the AppleID it should be associated with from the original owner, so you can then activate it with YOUR AppleID. Else it will brick up as per the Activation Lock and will be useless. See here on what the seller has to do: What to do before selling or giving away your iPhone, iPad, or iPod touch - Apple Support