1 oz Gold Bars. Proof & Mint Sets. 1987 Mexico Silver 12 Onzas US Constitution Proof (Box & COA). Photos in this listing may or may not be stock photos. The photos are meant to be an indication of the product you will receive. Contains 12 oz of Silver. Struck at the Mexico City Mint. Coins are packaged in a wooden box with a COA. Coin is in Proof condition. Obverse: Screw coining press below the date. Reverse: Franklin, Washington and Jefferson seated at a table signing the Constitution. Add this Mexican Silver 12 Onzas to your cart today! This is not a photo of the actual item.