What are Adjustment Marks on Coins?

Question: What are Adjustment Marks on Coins?

Adjustment marks appear on many pre-1840 coins, although they are most frequently seen on coins dated prior to 1821. These marks are sometimes confused with roller marks and other imperfections created during the coin minting process, but once you understand what caused adjustment marks, you should almost always be able to diagnose them for what they are.

Answer: Adjustment marks, also called weight adjustment marks, are file marks on the surface or edges of silver and gold coins minted prior to about 1840. Adjustment marks are most frequently encountered on U.S. silver coins from 1821 and earlier. The reason these file marks were made on the coins was to ensure that the coin was of exactly the proper weight.

Adjustment Marks and Overweight Coin Planchets

Prior to the early ninteenth century, the mint lacked the technology to create coin planchets of the exact specified weights, even though the law demanded that silver and gold coins be of precisely correct weight. The weight of the coin was especially critical at a time when the coin circulated at bullion value, rather than token value. Because the mint didn't have the technological capability to create coin planchets of exact weights, it would try to err on the side of too much, rather than too little weight. If the planchet was too light, there was no way to repair it, so it had to be melted down and recast.

However, if the coin planchet was too heavy, it could easily be fixed by using a metal file to file off bits of the coin metal until the correct weight was achieved. This filing effort left file marks and gouges on the surfaces of the planchets.

Effects of Striking on Adjustment Marks

The weight adjustment filing was primarily done before the coins were struck. When the coin striking actually occurred, the force of the strike would usually obliterate the file marks, especially on smaller and gold coins. Smaller coins came out better, with fewer remaining adjustment marks, because not as much force was needed to ensure that the metal flowed completely against the die surfaces during stirking. Gold coins came out better because gold is a softer metal than silver, so the striking force didn't need to be as strong to obliterate the file marks. Large silver coins such as silver dollars and half dollars didn't fare as well, and adjustment marks are often seen in the fields of early U.S. dollars and halves; occasionally, these file marks appear on the devices themselves.

Diagnosing Adjustment Marks on Coins

Weight adjustment marks are easily distinguished from roller marks, die polishing faults, die cracks, and coin cleaning marks by their characteristic appearance, although it might take the novice some time to develop an eye for this. The most distinguishing factor of adjustment marks are their non-parallel, sometimes willy-nilly appearance. Adjustment marks are usually deeper than roller marks, especially closer to the edges of the coin (whereas roller marks will usually be of uniform depth throughout.) Also, a few adjustment marks were sometimes made after striking, although this practice seems to have been rare.

For a fuller diagnostic on determining the cause of various markings on coins, especially roller marks and weight adjustment marks, (including photos of various types of marks), see Diagnosing Roller Marks and Adjustment Marks on Coins.