This is an interesting question that I have also asked myself. After some research, I found out that the supplier makes an order with several batteries inside in one box. When you buy one, you don't get sealed packaging. This also explains why they are cheaper than, for example, at a DIY store... It's up to you whether you want to pay a few francs more and buy a battery with packaging or choose this option. I bought mine here and I am satisfied.

So if a battery has been used before, you can see drag marks on the battery where it is inserted.