1, the beginning of Apple's serial number M indicates that the mobile phone is a genuine retail machine and a brand-new machine. The beginning of serial number n means that the mobile phone is an official replacement, the beginning of n means an official replacement, and the beginning of serial number f means that the mobile phone is an official refurbished machine; The beginning of the serial number P indicates that the mobile phone is custom machine. The official refurbished machine is officially recognized by Apple, and it is also manufactured in strict accordance with the factory inspection standards.

The fourth letter of Apple serial number represents the production period of mobile phone. K stands for the first half of 20 13; L stands for the second half of 20 13. M stands for the first half of 20 14; N stands for the second half of 20 14. P stands for the first half of 20 15; Q stands for the second half of 20 15.

3. The official machine change was because the iPhone was sent back to Apple for repair after a problem. The equipment brought back after the maintenance is called the official replacement machine. The official switch machine is also a brand-new machine, because Apple's assembly line basically produces a switch machine (beginning with N) for every 100 conventional mobile phones (beginning with M). It's just that these machines are only after-sales circulation and do not enter formal sales channels.