Basics of Coin Grading: Surface Preservation

Hello fellow numismatists. It’s that time of year again – March Numismadness!

In last month’s issue I discussed some of the basics of coin grading which was broken down into 3 basic categories, strike, luster and surface preservation. In this column I will go into detail about the coin grading factor of surface preservation, which is my favorite. I find it so interesting how many things can happen to a coin once it leaves the mint.

In years gone by when coins were stuck at the mint they were funneled into cloth bags. Imagine coins falling into a bag and clamoring against themselves thus creating marks and dings called bag marks. The larger the coin, the more severe the bag marks were. Many of these bags of coins were transported across the country and bore various degrees of handling and jostling in transport. At this point, the coins are still uncirculated but display varying degrees of imperfections. A novice often times makes the mistake of defining bag marks on a coin as wear. Wear only occurs when a coin has been personally handled, passed between people or has been in a pocket or purse for some time and moved around.

A sad fact of numismatics is the fact that for centuries people have cleaned coins. Older coins were made primarily of gold, silver, copper and nickel. Coins that normally reacted with outside elements are silver and copper. However, all coins can environmentally react to their immediate surroundings.

Unfortunately, it became commonplace to clean coins to remove any “discernable” tarnish or patina or crud. Coins are unique in the fact that cleaning them or restoring them actually hurts their value. This is true due to the fact that there are enough coins in original condition that haven’t been messed with, that cleaning a coin is detrimental to its’ value – unlike antique furniture and old cars. Cleaning a coin removes surface metal and that can never be reversed. However, an original piece of furniture or a car that is totally original and in mint condition is always worth more than a restored one.

Other factors that go into surface preservation is how coins have been stored. Coins that have been stored in the old Harco albums have a lot of pvc damage which was due to the plastic sleeves breaking down and leaving a green residue on coins. Except for gold coins, coins that have been in the ground normally have a lot of what is called “environmental damage” because the chemicals that are in the ground have a pitting effect on most coins. Many Shield nickels have environmental damage from being in the ground which corrode away most of the alloys in the coin except for the nickel. A lot of shield nickels have severe pitting because of this.

Spots on coins is another example of bad surface preservation. The coins that are most susceptible to spotting are cents which are made of copper. Copper is a highly reactive metal and it is not unusual to see “carbon spots” on them. They are called carbon spots because many times they are formed from carbon in the air or mishandling by people. Once a carbon spot is in a coin it is there forever and will leave a pit that actually grows deeper over time.

Even though copper coins are the most common coins to have spots, gold coins sometimes have spots due to the fact that copper was used as an alloy and if there is an area in the coin where the alloys weren’t evenly mixed, a spot can form where there is a concentration of copper.

In next month’s column, I will discuss another grading component – luster.

Chris Seuntjens,
Christopher’s Fine Jewelry and Rare Coins