The Origin of Mint-Made Defects on Bullion Coins
Contrary to popular belief, not all coins leave the Mint in “MS 70” condition. A common misperception is that all coins start out flawless and begin to acquire blemishes and issues upon release. In actuality, some coins are imperfectly made and/or become flawed before leaving the US Mint. Regardless of how or why these defects occur, they nonetheless can detract from a coin’s grade and market value.
The first opportunity for error takes place when the planchets (essentially a fancy word for “blanks”) are made. Planchets are meant to be perfectly smooth and round before striking, but in rarer cases they can become misshapen, uneven in texture, marked, cracked or even porous. While many of these minor imperfections disappear during the minting process, sometimes the planchet flaws remain visible after striking. This was especially true in the late 18th and early 19th century; many planchets were poorly made with their defects still plainly visible after being struck.
Speaking of mint-made defects from the 18th and 19th century, another common phenomenon was the presence of adjustment marks. Found mostly on pieces dated between 1794 and 1820, these parallel cuts into a coin’s surface were an attempt to correct coins that were overweight. Rather than melt the coin down and start over, Mint employees would shave a tiny amount of metal off the coin. Most adjustment marks are minor and do not detract from a coin’s appearance, but some are harsh and are severely distracting.
In more recent years, planchets have become more uniform in their weight and size—but a new type of mint-made defect has developed. Some world mints are using washes and lubricants to make the coins look better and easier to strike. By washing the planchets before striking, the coins generally look better and the chance of foreign objects sticking to the metal is reduced. The lubricants make the coins easier to strike, thus speeding up the production process.
While these substances generally improve efficiency and aesthetics, they have a potential negative downside. If some residue is left remaining on the coin, it can result in haze, milk spots or ugly toning. There are many modern coins that have immaculate surfaces but exhibit detracting discoloration. Even without being touched by human hands—or even before leaving the mint—these coins have already acquired defects.
A distinction should be made between mint-made defects and errors. The former category is mostly detracting flaws that take away from a coin’s grade, appearance and/or market value. This should not be confused with mint errors, the majority of which are highly collectible. The most spectacular mint errors are actually wildly valuable, whereas the most extreme mint made defects are frowned upon. Milk spots, planchet cracks and adjustment marks are frowned upon, but extreme errors like off-center coins actually command a premium in the marketplace.