Coin Grading - AU or BU: Understanding the Difference

By Peter Mosiondz, Jr. for CoinWeek …..

Coin grading practices are based on common sense aided by experience. In many instances, the difference between two grades can be a significant amount of your hard-earned money. This is especially true comparing the prices of About Uncirculated (AU) and Brilliant Uncirculated (BU or Mint State) coins.

Plainly stated, a coin is no longer BU or Mint State if it displays any wear or rub.

It’s no secret that many coins having some degree of wear or rub look at first glance to be Mint State. We’ll briefly touch upon both wear and rub.

But how does one determine if the coin has wear? That’s easy: look at the high points. And what are the high points? The highest points of a coin are those areas that rise up more than the other areas of a coin. In the case of a portrait coin, the highest points would be the hair, the ear, and the cheek. Each coin is different though because of the differences in design.

It’s also important that you look for discoloration in the area of the high points. Each coinage metal changes in color a bit differently after experiencing wear, friction, or rub. Here’s a handy chart to help you.

  • The high points of copper coins turn a darkish brown.
  • The high points of nickel coins turn a dark gray.
  • The high points of silver coins turn a dull gray.
  • The high points of gold coins turn dull or dark gold.

Wear on the high points will almost always feature this discoloration. Additionally, the mint luster will be interrupted on a coin that has wear, friction, or rub. This is not the situation with Mint State coins. They will always feature uninterrupted mint luster.

When attempting to distinguish a Mint State coin from one that is About Uncirculated, nothing can be more difficult to find than a “rub”. “Rub” is a term used to identify a very small area on a coin that shows evidence of having seen circulation, no matter how briefly. It can easily come about by improper handling. Rub is basically slight friction resulting from the coin’s having been in circulation, even as a pocket piece.

The experienced numismatist takes ample time to properly evaluate all coins very closely during the buying process. To parody the saying “Haste makes waste”, I would say that “Haste makes waste… of your pocketbook”.

highpointswearOnce you’ve mastered the differences between About Uncirculated and Mint State you will have defended yourself against unscrupulous sellers attempting to sell you About Uncirculated coins as Mint State examples.

Of course, with the advent of third-party coin grading and encapsulation services, these fears are virtually eliminated. The key word being “virtually”. Remember that we’re all human and we all make mistakes. This applies to third-party grading services as well. If you’re like me, you may wish to purchase “raw” or unencapsulated coins from time to time. I want to make sure that I am well prepared to assess any potential purchase very carefully.

As to magnification, I have used a 5x lens for many years. The “5x” means that the coin and elements on the coin are magnified five times the actual size. It’s best to view the entire coin first when looking for wear and, if something attracts your eye, view that particular area very carefully.

Toned coins can present a problem to the untrained eye. Some, in fact, can be very deceptive. This is especially true when we become mesmerized by a beautifully toned coin displaying several magnificent colors. And these colors will most likely appear on the high points. No doubt you’ll skip right over the high points at first – I know I do. Admittedly, in this instance wear is almost impossible to detect.

Notice I said “almost”. Look long and hard and, with experience, you will see the wear if it is indeed present.

Be particularly careful with gold coins.

Just about every gold coin “looks” Mint State at first or even second glance. This is because gold coins retain some mint luster indefinitely. As with all coins, a gold coin that is not Mint State will show wear, friction, or rub and will not display the uninterrupted mint luster that is absolutely necessary for a coin to be classified as Mint State.

I hope this brief discourse has been of use and that you will become more proficient in your coin grading and, therefore, buying tendencies. After all, it’s your money.



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