How do you glue a penny?
A. Clean the pennies well before adhering them, try Silaprene adhesive. A. Dip the pennies in vinegar for a few minutes to clean them, let them dry and then glue them together with epoxy resin (e. g., Araldite). Avoid epoxy adhesive if you want a reliable bond. Copper reacts with epoxy (or more correctly the hardener).