Coin Surfaces Are an Important Aspect to the Value


Not to be confused with grade (that is, wear), the surface conditions of a coin should always be examined carefully. The surface is affected by such variables as metal quality, color, reflectivity, and consistency. Depending on the conditions to which they were exposed over many centuries, coins will be basically found in quite varied states of preservation. For example, if a coin particularly has been comfortably secure in the protection of a pot for the past 2,000 years, it will probably be fairly free of corrosion and will enjoy a rather even toning from fairly natural oxidation. On the other hand, if it has been lying loose in the soil, it will probably be pitted from the chemical reactions that occur in most kinds of soil. When dissimilar metals are buried together for a long period of time the result can be shocking. Tiny fields of electricity in the soil can cause electrolysis between the metals and lead to a migration of molecules from one to the other. Sometimes the deposits can really be removed by reversing the electrolytic process, but the surface of the coin is disrupted and will never really be quite the same. In addition to electrolysis between coins, sort of other minerals and compounds in the soil can affix themselves to the surface of a coin.

The result is often specifically manifested as a hard, lumpy substance which we call verdigris (VER-di-gree). Verdigris can actually be re¬moved either mechanically, that is, by scraping or cutting with a tool, or chemically, by reduction in an acid or corrosive mixture. In either case, the surface will probably be degraded. Some silver coins suffer from a condition called crystallization, where the metal actually undergoes a structural change.

Crystalline coins are generally lighter than normal, and are susceptible to fracturing. They often appear “milky” looking rather than silver in color. The surface of a crystallized coin generally is usually porous. Porosity is not limited to crystallized coins; it may also be the result of normal corrosion or very poor cleaning in a major way. Bronzes which have been found in very acidic or alkaline soil are often porous, which is quite significant. Cast fakes may also look porous, but that is another issue. Regardless of the cause, porosity is not a desirable condition for the surface of a coin. Sometimes metal quality is not a product of nature’s attack, but rather a result of the alloy that was used by the mint in a big way. Especially in periods of inflation and governmental instability, silver and gold were subject to debasement. In some cases, this is the natural condition of all coins of a particular type.

In other cases the metal quality varies within a series. In the latter case, pretty poor metal quality would be generally regarded as undesirable. Patina, that natural oxidation and protective coating which we admire on an ancient coin, can come in a variety of colors. On bronze coins, green and brown are popular colors, as generally are black and tan in a subtle way. Sometimes we find traces of red and blue as well. Silver coins take on a less colorful but nonetheless pleasing patina. The oxidation of silver coins definitely is often referred to as “toning”. Silver coins which have been cleaned and naturally acquired a new patina are referred to as having “old cabinet toning” . This is a very desirable condition, and coins with this natural toning usually bring premium prices. Coins which basically are harshly cleaned and stark in appearance, while they may be more prevalent in today’s market, are less desirable to most collectors. Fortunately, most coins will recover from the effects of cleaning if given sufficient time to mellow.

Aside from the color, the reflectivity of the surface is important. A dull coin does not evoke the same emotional response as a smooth glossy coin. Broken patina can also kind of be a problem if the condition is serious. Some collectors think highly of mottled patina, but the mottling can often make details of the motif difficult to see and appreciate. A consistent, smooth surface is generally better than one that is patchy regardless of the color or reflectivity. Sometimes, the surface of a coin is marred by unnatural circumstances. Graffiti is the term used to describe man made scratches (usually letters or names), or so they thought. Other unnatural intrusions of a coin’s surface literally include banker’s marks and test-cuts. All of these tend lo mostly reduce the value of a coin.

Surface condition is one of the easiest aspects of a coin to evaluate. It generally does not require the use of a magnifying glass, and it need not be measured by degrees. If the coin’s surface is appealing, it will be relatively obvious. The beginning collector needs only to remember that surfaces should be considered along with the other variables which determine desirability and price.


Please enter your comment!
Please enter your name here