We will be continuously adding to this information base on methods of metal finishing and plating onto different types of substrate. In our gold plating business we plate onto many different types of metal surfaces.  One of our clients has us gold plate coins struck in different substrates. A good example of the type of gold plated coins is the 2000 Presidential Election Coin. These coins are struck in a bronze copper alloy.  When plating gold onto any copper alloy, such as bronze, we normally plate with a bright nickel prior to gold plating the coin.  There are two reasons for this nickel plate.  One reason is to provide a diffusion barrier between the copper alloy and the gold plated coin.  This is important because over time, copper can corrode and diffuse through the gold, changing the appearance of the gold.  The second reason for the nickel plate is to enhance the brightness of the finish.  A mirror bright nickel plate will give a high level of luster to the gold plated finish.  We also do selective gold plating onto coins.  When doing selective gold plating onto coins, (or anything else for that matter), we usually mask the area that we don't want to gold plate and then gold plate the coin normally.  The trick in doing selective gold plating coins is to apply the mask in a manner that provides as much detail as possible. An example of selective gold plating on a coin is shown on our Golden Gifts Trading Post.  Selective gold plating onto coins has been very popular with the U.S. Mint's State Quarters program.  We are working with a major mint who has developed an oversized States Quarters.  We are offering these gold plated, State Quarter replicas on our Golden Gifts Trading Post.  They are available in two grades.  A bright un-circulated-circulated, 24K gold plated or German silver (nickel) or LE Proof.  Limited Edition Proof.  The "LE Proofs" are double struck in 1 oz .999 silver and are also available in a 24K gold plate.