Penny trays are found in convenience stores and markets all around America. Some are commercially fabricated while others are hand made. There is no law or formal rule applied. If one has extra, they pay it forward. Someone else finds willingness to accept help and takes it. One doesn’t know if the person who left the penny was “good” or “evil” and it isn’t clear how the penny will be used at all. This unwritten contract seemingly built on kindness persists.