The sticker will be inside the helmet it will either be M or SA and a year (95,00,05). You should also find build date. For instance, my helmet was made in '97 built to SA95 standards. Time for me to get a new helmet.
If you are getting a helmet, you can find '00 helmets about $30-50 cheaper, but they will be out of date in 2012. '05 helmets will be out of date in 2017.