Coin Update contributor Louis Golino recently wrote an article providing the known information on the 2010-P Grand Canyon Five Ounce Silver Uncirculated Coins that some collectors and dealers had received with unusual surface finishes. The US Mint has provided a statement explaining the inconsistencies encountered.
All numismatic versions of the America the Beautiful Five Ounce Silver Coins are vapor blasted after the coins have been struck. This process involves using water vapor and ceramic media mix and is similar to sandblasting, but water vapor is used instead of compressed air. The process is supposed to provide a uniform, protective finish on each coin.
Some coins have been received by collectors which have a "light finish" or which completely lack the finish on one or both sides of the coin.
The statement from the United States Mint on this situation follows:
From photographs we have received, and reports from coin grading services, it is apparent that several varieties of America the Beautiful Five Ounce Silver Uncirculated Coins exist with differing or missing vapor blast finishes. We are looking into the cause of the inconsistency in finishes, examining each step in the post-production process when vapor blasting is applied. We are committed to restoring the consistency for which United States Mint products are known worldwide.
While we have ordered new equipment to execute automated vapor blasting on the America the Beautiful Five Ounce Silver Uncirculated Coins, we are currently using the process originally used for our 3-inch medals. That equipment required retro-fitting and readjustment for the process, and has required additional maintenance due to the higher volume and substantially increased wear of this program.
The new equipment will allow us to move from the manual, batch process to more closely integrate the vapor blasting application into the overall production line for the coin.