Grand Canyon coins lack post-strike finish
- Published: Jul 18, 2011, 8 PM
An uncertain number of Uncirculated 2010-P Grand Canyon National Park 5-ounce silver coins missing the post-strike finish were shipped by the U.S. Mint to customers who ordered the numismatic coins.
U.S. Mint officials were unaware that Mint had released coins missing the post-strike finish when contacted July 13 by Coin World.
Minnesota collector Aaron J. Gelner reported to Coin World on July 12 that his local barber, Tom Schneider, had received two of the Uncirculated 2010-P Grand Canyon National Park 5-ounce silver coins that day, one with the post-strike finish and one without. Images of the two coins taken by Gelner are illustrated with this article.
Connecticut collector Jim Scroggins on July 13 also reported to Coin World his receipt of an Uncirculated 2010-P Grand Canyon National Park 5-ounce silver coin missing the post-strike finish.
Unlike the bullion versions of the 5-ounce coins struck at the Philadelphia Mint but intentionally without Mint mark, the numismatic versions are produced with a P Mint mark on the reverse. The Mint-marked numismatic versions also are supposed to receive a post-strike finish.
The same ready-to-strike 5-ounce planchets received from supplier Sunshine Minting from Coeur d’Alene, Idaho, for the bullion versions are also used for the Uncirculated numismatic versions. However, the numismatic coins undergo a “vapor blasting” technique after striking, resulting in a finish replicating that used on 3-inch bronze Mint medals, according to U.S. Mint spokesman Michael White.
“The machine uses a water vapor and ceramic media mix,” according to White. “It is similar to sand blasting, but instead of using dry compressed air [propelled at high speed], it uses a compressed wet vapor. The finish is applied to the coin after striking and not to the die. This will provide a consistent coin-to-coin finish.”
Before striking, the ready-to-strike planchets exhibit prooflike surfaces. ¦
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