Zinc alloy castings offer the advantage of lower cost. The quality is relatively good, but if carried as a pocket coin, the patina (finish) tends to wear off exposing the base metal. While a die struck bronze or brass coin is more expensive, the result renders a far superior product and being solid brass the finish does not wear off. Zinc alloy is used to reproduce items that are not easily made by the die struck method such as the bottle opener or airborne wings shown. The cast alloy coins are also lighter in weight than the brass coins.