A burnished metallic object has the characteristic of being smooth and bright. This effect is created by rubbing or polishing. Coins with this characteristic will have a bright matte-like finish, appearing dull or lacking luster when displayed beneath a warm light source. This condition may or may not affect the coin's value, depending on what collectors find to be ideal---and whether the burnishing was done artificially or at the mint.
Burnished coins have an artificially polished surface that is generally considered to be detrimental to the value of the coin and should be mentioned in its description. A coin collector may burnish a coin that has been tarnished or marred by poor storage conditions or prior circulation, in an effort to improve the coin's look and feel, with the mistaken belief that it will increase the coin's value.
Authentic Burnished Coins
Some coins come straight from the mint with the burnished effect. In 2006, according to eBay Guides, the U.S. Mint produced platinum, gold and silver coins that were burnished. The key difference between these coins and artificially burnished coins is the coin blanks were burnished prior to being struck with the die. These coins are identified by the "W" mint mark, meaning they were struck at the West Point Mint.
American Silver Eagles
Brought into production in 1986, the American Silver Eagle is the official silver bullion of the United States, containing one troy ounce of .999 pure silver. In 2006, a version called a "burnished strike" was added to the proof and mint state varieties. It is important to note that the value of this coin is neither improved nor diminished by the burnished effect. Its value is determined by the market trading price of silver bullion, as well as the condition and rarity of the coin.
The Burnishing Process
Coins and planchets (blank metal disks ready to be struck with a coin die) can be burnished by buffing the coin or blank or by using a wire brush, often on a high speed drill. The buffing method, primarily used on planchets, will produce a mirror-like appearance, while the wire brush technique achieves a matte-like finish---a look commonly found on refurbished coins.