battery markings/date

[DKL]

My Bosch silver battery seems to have given up the ghost. Now I know the last chap bought it and he bought the car in 8/08. These batteries have a 4 or 5 year guarantee but of course I don't have a receipt.

So does anyone know if:
the guarantee is valid at any Bosch dealer
can they tell how old it is by the markings on the battery itself?