Hello, there is no stock machine for Apple products. Look at the iPhone6. Apple stores in the United States are already in line. The stock machine is a statement made by some merchants to deceive consumers. There is no serial number information, which means it is a black machine, a machine of unknown origin, a fraud machine, a revision machine and so on.
You can use the serial number to go to a third-party website or official website to simply check the equipment information.
How to find the mobile phone serial number: Settings-> General->; About this machine->; serial number
Query website: /appleinfo/