NGC Ancients: Surface Quality Important for Ancient Coins

Posted on 1/20/2015

The evaluation of surface quality is paramount to establishing the overall quality of an ancient coin.

Surface quality plays a significant role in establishing the desirability—and, hence, the value—of coins to collectors. For this reason, NGC Ancients evaluates the quality of a coin’s surface separately from its grade and strike. It is rated on a scale of 1 to 5, with 1 being the lowest and 5 the highest; since each point represents a 20 percent portion of the scale, those designated a “5” need not be perfect, for that rating incorporates the top 20 percent of the scale.

With the exception of circulation wear, our surface rating takes into account all factors that affect a coin after the moment of its creation. These may be segregated into the three main phases of the “life” of an ancient coin: circulation, burial and recovery/conservation. Foremost among these factors are patina, corrosion, encrustation, cleaning, marks, and even the presence of original luster.

Assigning a surface rating requires the experience of having handled tens of thousands of ancient coins, for what is a normal surface condition for one type may be unusual for another, and that must be taken into consideration. Gold and silver coins, for example, often survive with lustrous, nearly perfect surfaces.

To investigate this subject more thoroughly, we’ll study a few coins with notable surface conditions.

One especially desirable surface condition is the presence of “silvering,” a thin layer of silver on the surface of base metal (or heavily debased) coins. Attempts sometimes are made in modern times to add silver to a coin’s surface to simulate this condition, but this is unusual since so many Roman coins survive with traces of original silvering. This billon nummus struck at the mint of Siscia for the Caesar Constantius I in about A.D. 301 retains most of its original silvering, making it highly desirable to collectors.

Ancient silver coins often were tested by merchants to determine if they were of good silver or were plated counterfeits. The surfaces of this silver tetradrachm of Athens, struck early in the 5th Century B.C., are disfigured by two test cuts. Not only did they cut deeply into the obverse, but, in the process, the chisel marks flattened elements of the reverse design.

A more interesting form of surface marking occurs in the form of countermarks. While the application of a countermark may have—inadvertently—revealed whether a coin was genuine or silver-plated, the main purpose of these markings seems to have been for approval, re-valuation, or some related goal. This silver drachm of Aspendus, in the region of Pamphylia (in Southern Turkey), from the late 5th or early 4th Century B.C., has three distinct countermarks on its reverse, each bearing its own design.

During their long periods of burial, silver and copper coins usually suffer some kind of surface damage from surrounding water, soil or agricultural chemicals. Usually this is in the form of granularity, corrosion or porosity. This silver denarius portraying Julius Caesar has small pits on its surface; though it reduces its value to collectors, it is still a desirable piece.

Ancient bronzes often are affected adversely by burial; other times, however, they acquire remarkable patinas that greatly enhance their appeal to collectors. Since the surfaces of bronzes often are heavily encrusted, efforts sometimes are made to remove that build-up. Occasionally these efforts go too far, as with this bronze sestertius struck for the Emperor Septimius Severus soon after his death in A.D. 211. Its fields are heavily smoothed, which reduces its market value.

Another surface condition worth describing is the alteration or the strengthening of details. Typically, coins affected in this way are rejected for grading by NGC Ancients. On this bronze sestertius of Lucius Verus (A.D. 161-169) the details of the emperor’s hair, wreath and beard have been ‘strengthened’ by an enterprising individual who attempted to increase its market value.

Since it’s always best to end on a high note, let’s examine this silver denarius struck for the Emperor Antoninus Pius (A.D. 138-161). Its surfaces are essentially unimpaired and it would merit a 5 out of 5 rating – enough to please even the most advanced collector.

Interested in reading more articles on Ancient coins? Click here

Images courtesy of Classical Numismatic Group, Inc.

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