I've read that the FPO number is not unique. Sorry if this question is stupid for you but... Can there be more than 1 processors with the same FPO numbers?
Correct, it is possible that processors share the same FPO numbers.
Note the picture below;
The serial number is a mix of the FPO number and the ATPO number. The ATPO is a unique number. For example, you can find a processor with the same FPO number as yours but it the ATPO number will never match.