What is Coin Luster?
Coins in pristine condition are often described using the terms “shiny” and “flashy.” Those words specifically refer to a coin’s luster, or the way the light interacts with the coin. Luster has a significant impact on a coin’s grade, eye appeal and market value. It is a positive feature that can take on a number of different appearances, depending on how the coin was manufactured. In fact, certain types of luster are considered exceptionally desirable. This article will describe why luster exists and the various types of luster seen on United States coinage.
Coin blanks, generally speaking, have a mirror-like quality. Their surfaces tend to be extremely smooth and thus they have a somewhat flat, reflective appearance. Once the blanks are struck with dies, the metal shifts quickly as it fills the voids of the die. This metal flow creates microscopic grooves and striations; this metal movement is what creates luster. Generally speaking, the more complex the design of the coin, the more the metal will flow (and thus the more lustrous the coin will become).
A number of different luster patterns and types exist, depending on how the dies were prepared, the type of metal used, the format of the design, the age of the dies, etc. Brand new dies have a tendency to create “prooflike” luster, where the surfaces are reflective like a proof coin. As time goes on the dies are more likely to produce coins with frosty, satiny luster. Harder metals, like nickel, are less apt to flow and are more likely to have subdued luster. Gold and silver, meanwhile, tend to display stronger and flashier luster.
Once a coin is released into circulation, its luster can quickly diminish and fade. As a coin is rubbed and worn, the tiny metallic grooves become smoothed over and dulled. The open and unprotected areas are typically the first to lose luster, while protected sections near major design features remain flashy after some time in circulation. Heavy toning can also veil or mask luster. If a coin is stored in a chemically reactive environment, the surfaces can take on a flat and muted appearances.
In addition to affecting a coin’s appearance, luster can also impact a coin’s grade. If a coin is on the fence between two grades, it will get the benefit of the doubt (and the higher of the two grades) for having exceptional luster. Conversely, a dull, lackluster coin can be penalized quite a bit. This reward/penalty is amplified for coins that are known to have superb luster—or typically seen with drab surfaces. Early coins tend to be lifeless and bland in appearance, so luster will significantly boost their grades. On the other end of the spectrum, Mercury Dimes almost always display fantastic luster, so anything short of that will knock a coin’s grade.
Simply put, luster is an important aspect of a coin’s appearance, grade and price. While these metal flows are microscopic, they can (and often do) have a not-so-microscopic influence on its aesthetics and value.