just wanna contribute something. Attached is a BIG high resolution picture taken from my original nokia battery.
original nokia stickers will have micro printing on it.
Note the very very small 'NOKIA ORIGINAL' word repeatation around the circle of the NOKIA logo. Immitation nokia stickers cant immitate micro printing.
However do take note that original stickers still doesnt guarantee the originality, as kit_kit mentioned, original stickers can be bought.

cheers.

battery become bloated due to manufacturing defects and/or improper charging cycle etc etc.. usually when it's bloated, its a gone case already. Send for warranty if u can.. if not, buy new one la.