wet_blobby said:

I still cant see how the letter at the end of your PO number can be anything else but random, I know tallying up with a formula has been mentioned but, my mate who joined the same day as me, has the same letter of the alphabet starting his surname, and his Po number is One number higher than mine, yet the letter at the end of his number is completley different, not even the next letter of the alphabet. So I remain unconvienced unless someone can shed more light on the "formula" used.

Say for example, you have (like me) 1 letter, 6 numbers, 1 letter in your number.

The algorithm may be something like:

1st number x 2nd number + 3rd number divide by some bizarre constant like 13.4 x 4th number - 5th number x another constant (say, 99.957) + 6th number

When you put all the numbers in, then the number that pops out should be between 1 and 26. If it is 5, then the letter at the end will be E and so on. This way, they know that your number is real and not fake.

It's not totally random, it just looks it since even if your Oppo's number is only different by 1, then your end letters will be completely different. Using checks like this is pretty common - used in a lot of things like bank accounts, ISBN numbers, Credit Card numbers . .

Just to point out that the example I used is just for show - no idea what the original one is like, but probably a lot more complicated.