I was using both types of silver. But even when I use authentic 1920s silver dollars a single coin scans very high and clean, but if I stack even two together the sound and numbers change drastically towards a junk/broken signal with lower numbers. I was mostly joking about large piles of coin. But two together I think is common enough that I want to figure out if there is a simple way people adjust anything to deal with this or like you stated, do I just need to get more practice and learn this feature.... thanks.