What Is Burnished Coin?

Burnishing Defined

• To burnish a coin means to polish the surface. The intent and timing of the burnishing will yield very different results. The burnishing of a coin prior to the striking -- the minting process -- is performed to create a highly polished surface or specific design background. Burnishing following the strike of a coin is used to clear the rust, or patina, from a coin and can sometimes significantly degrade the appearance and value of the coin.

18th Century Burnishing

• Burnished coins available in the 18th century were specifically minted for the purpose of creating proofs or special editions. The process of burnishing occurred before the planchet was struck during the minting process. The burnishing process in the 18th century utilized wet sand to polish the planchet to a high gloss. Burnished coins, once struck, had a significantly higher shine in areas not directly affected during the striking process.

Restorative Burnishing

• Restorative burnishing is typically considered a nondesirable restorative method. A variety of methods are used to remove the patina. Surface scratches actually remove some of the original metal during the process. High-speed drills and buffing pads are commonly used to create a high shine or luster on coins. Burnished coins are considered restored coins and are not as highly graded as original burnishing.

Modern Burnishing

• Modern burnishing processes, like during the 18th century, are performed on the planchets prior to the strike process. Machine buffing of the blanks yields mirror-like surfaces for striking proof and special-editions coins.

  As an example, American Eagle proof coins are produced using a burnished blank that is manually fed into the striking machine by handlers using white gloves to avoid marring the surface with oils from the skin. The coin is struck multiple times. According to the U.S. Mint, this process yields a coin that is "softly frosted, yet detailed images seem to float above a mirror-like field."