You have a
sticker in one of the books that identify your car (like the vin number)
I think that by this age of car, all records will be in digital form only, so the paper service handbook/record where the second build
sticker has fixed is no longer supplied.
Rumour has it that at least VW Golf, have this build
sticker hidden under the plastic trim panel just inside the hatch area - how clever is that if it is true!
Other way to source this information is to ask your local SEAT dealer for a print out of CAR DATA, that document contains this information and a lot more about that specific car, even actual build date in most cases.
Edit:- CAR DATA is found within dealers workshop parts system and maybe in their workshop repair manual system. So the first place to ask for it should be the parts department.