1. The secret in numbers

Click on Settings--General--About this machine, and we can see all the information in the machine. There is a setting in the machine. Serial number, this serial number is very important for iPhone 4. The seemingly irregular combination of numbers actually reveals the birth date of iPhone 4.

The serial number on this machine is 5k1175. We only need to look at the third, fourth and fifth digits. The third digit represents the year of production of the mobile phone, and the fourth and fifth digits represent the weeks in which the machine was produced. If this machine is from the 17th week of 2011, we can roughly calculate the price you bought. How long has the machine been produced? The third digit is 0, which of course means that this machine was produced in 2010. If you find that the production date of the mobile phone you purchased is quite far away, and even the third, fourth, and fifth digits of the serial number of some knock-off phones are not numbers but English letters, then you should consider whether to buy a refurbished phone. Or fake.

2. Digital reminder

In the dialing interface, press the digital serial number of "* # 0 6 #" in sequence. This set of numbers must be exactly the same as the numbers on the phone card slot. , can the true identity be verified.

3. The writing on the back cover

The trademark information is marked on the back cover of iPhone 4, but if you compare it carefully, you will also find that it is different. There are Chinese characters on behalf of the machine. It means it is licensed from mainland China, and the word "china" means it is licensed from Hong Kong.

Go back to the interface where you just searched for the serial number. In the model column, if the last two letters are CH, it means that the machine is licensed in mainland China, and if it is ZP, it means that the machine is licensed in Hong Kong. Be careful if you find that the mark on the back cover and the serial number are not correct.

4. Information in the screws

The only two screws on iPhone 4 need to be carefully observed. Some are cross-shaped and some are torx-shaped. Apple's early products used cross-head screws, which were easy to refurbish. Later products all used torx screws that were not easy to find. The torx screws are very new, polished and bright, without any scratches. These two screws can also be a breakthrough for you to identify a refurbished machine. If you buy a machine that is said to be new but has cross screws, there must be something wrong inside. In addition, it is not difficult to see whether the screws have been touched and whether they are polished.