Bob, I think and could be wrong, the op is asking about the part number located in the serial number. Example:
Serial Number: ******
2888******
Part Number: 03G-P4-2888-KR
This is the same on all of my. Registered GPU's.
There is 6 digits, a part number, and 6 more digits.
Power supplies have a slightly different part number in the serial number.
Serial Number: ******
1608******
Part Number: 120-G2-1600-X1
All psu's have an 8 at the end of the serial numbers part number.
I have removed the rest of the numbers as they are not actually relevant. You will see the pattern if you look st your products in your profile.