There is still a serial number printed on the box, and a batch number on the box AND heat spreader. A part of the serial number (assembly test process order nu

There is still a serial number printed on the box, and a batch number on the box AND heat spreader. A part of the serial number (assembly test process order number) is also printed on the CPU package (not the box, but the actual die carrier). So, even if the counterfeiter made the effort to replace the heat spreader, you could still find out. Edit: Talking about Intel CPUs obviously.