Review on Smart Digital Capacity Tracker Stickers by Jerry Olson

An excellent idea, it seems to have been adequately executed. However, brand new batteries died within a week of installation. The second new set also died within a week. Not sure if I'm doing something wrong or if I have a higher performance bug, but the battery drain means it's not very useful for real coin counting. However, it holds up well. Also, as another reviewer noted, the drop-in spring is quite firm, making it easy to miscount if you don't insert the coin all the way in and it bounces back toward you.