Each CPU should have a serial number, problem is I dont know if that can be checked via software or if you would have to physically inspect the chip.
I am pretty sure each CPU has a serial number encoded into it.
I saw a video of the fake i7s and I can tell you that from the box alone it looks fake. The fan looked to be made out of rubber or foam and so did the CPU.
Sad to see people trying to rip PC people off.