What Are Hairlines and How Are They Caused?

Posted by Skip Fazzari, Authentication Consultant to NGC, on 9/15/2008

Skip Fazzari delivers a crash course in distinguishing this special defect, and how it affects grading.

Many of the silver coins that we receive at Numismatic Conservation Services (NCS) are heavily tarnished. Dark tarnish can hide the underlying surface of a coin, making it almost impossible to see the change of color and hairline scratches characteristic of improper cleaning.

If you will look on page 22 of the fifth edition of the Official A.N.A. Grading Standards for US Coins, there is a chart describing the attributes for each Mint State (MS) grade (this chart is missing from the sixth edition). These descriptions serve as guidelines. For example, with respect to hairlines, the grading guide states that an MS 61 coin may have noticeable or continuous hairlining on its surfaces. For a coin to grade MS 66 or higher, there should be no significant hairlines visible without magnification.

So what exactly is a “hairline” and how are they caused? Are they all from improper cleaning? Hairlines are minute scratches to a coin’s surface. They are best seen on Proof coins. It is not unusual to find a few hairlines going in random directions on almost any coin. Any hard particle, such as mineral dust or grit that comes into contact with a coin may cause these tiny random scratches. When they are few and far between or in hardly noticeable places their impact on a coin’s grade is negligible. Hairlines become extremely detracting when the lines are parallel, very close together, and extensive. On coins that are heavily cleaned or damaged by counting wheels, the hairlines become so close that the surface appears polished.

The best way to see hairlines on a coin is to tip and rotate it under an incandescent or tensor light in an otherwise dark room. Another technique used by some is to hold the suspect coin far away from the light, down in the shadow between your knees. As the hairlines become perpendicular to the light, the coin will suddenly “flash” back at you as you examine it. This method is especially useful to detect the “wipes” when a rotating rubber counting machine wheel has damaged the coin’s surface. Coins with counting machine marks are rarely found in slabs because they are considered “problem” coins.

Since so many collectors of Uncirculated coins search for examples in the MS 63 to MS 65 range, let’s focus on the grade chart between the two examples of hairlines I have taken for MS 61 and MS 66 coins. One step in formulating the grade of a coin is to be aware of the highest grade a coin can attain considering the amount of hairlines present. Easily seen hairlines are tolerated and even expected for grades of MS 63 and lower. If the hairlines are not detected, these coins will look to be a much higher grade and a novice collector who is judging a coin by its number of bagmarks alone will feel that the coin is under-graded.

For MS 64 and MS 65 coins, it’s the number and location of the hairlines that determines the grade. In many cases, a small patch of hairlines is all that is needed to drop an MS 65 coin one grade.

Less experienced collectors may confuse mint-made die polishing marks for hairlines. Die polish lines are raised on the coin’s surface. Hairline scratches on a coin go down into its surface. This difference may be difficult to see at first. Obviously, if a collector does not detect the hairlines on a coin or mistakes them for die polish, he might be tempted to remove it from a slab to send it in for a higher grade. This can be a quick grading lesson when the coin is returned with its original grade.

This article previously featured in Numismatic News.Many of the silver coins that we receive at Numismatic Conservation Services (NCS) are heavily tarnished. Dark tarnish can hide the underlying surface of a coin, making it almost impossible to see the change of color and hairline scratches characteristic of improper cleaning.