I'll repeat my personal viewpoint. I don't clean if I am trading or selling. Let the buyer decide what is best for their collection. For my own that I keep, if it's moderatly dirty, I leave it alone, if it has deep grunge I used a soft childrens tooth brush and window cleaner. ps hot stamps will turn from gold to silver, so they get covered with my thumb and I only clean the mold designs. Chipco, Paulson graphics BJ and others of like design are much more durable.