As the article mentions, the battery is likely a Zamboni pile, which has an extremely high internal resistance (i.e. can only supply very low currents) but is made for high voltage, electrostatic applications like this bell. That's why it lasted so long - modern battery chemistries have much lower internal resistance, and self-discharge would mean it being completely depleted in much less time. The battery in this bell has such high internal resistance that the self-discharge is many orders of magnitude less.<p>The characteristics of these batteries are different enough that you'll find lots of claims of "perpetual motion" on the Internet from people who have made them and found how long they can last when powering low-current loads like LEDs!