Default [Q] Mainboard part number

Hi,
I recently bricked my TF300T and now I am looking for a replacement mainboard. Op carefully disassembled the tab and found the following part number: 60-OK0GMB5000 - A812490091AKS1A

Now on eBay I can find the 60-OK0GMB5000, however I noticed that some retailers also distinguish in the first three digits of the second part of the part number, namely A81.

What is the difference between for instance A23, A31, A81 and A91? Are the country codes or something.

For your information, I am from the Netherlands.

Thanks in advance.