Free Button Cell Batteries

Where I live we get an advertisement in the mail once in a while from a local auto dealership. The advertisement is a gimmick to get people to come to the dealership. It consists of a big sheet of thick paper with a combination box attached to it. The combo box has a number on it that is revealed by pulling a tag out of the box. The box has batteries in it and lights up to reveal the numbers when you pull the tab out. 

If you pry the box open, there are button cell batteries in it. If you use this type of batteries, you can collect these ads from friends and family and stock up on button cell batteries for free.