LWC Grading Question

An AU (About Uncirculated) coin does not have to have mint red or red-brown surfaces. It can be 100% brown and still grade AU or higher.

I am not exactly sure if the question has to do with mint luster or color since they are two separate things. I guess I'll try to answer both.

On gold and silver, an AU coin typically retains some of the cartwheel luster but on copper coins, I don't usually see much of cartwheel. They can still grade AU or MS depending on how much wear.

The vast majority of AU copper coins that I have seen are fully brown with a few that still have a little bit of the original mint red usually cling around the devices. An circulated copper coin should not look almost completely orangey red as that is a very good sign that the surfaces have been messed around with. Contact with fingers, dirt, and the environment while in circulation begins to react with the copper very quickly turning the surfaces brown.

Luster is imparted by the metal flow lines which are very delicate. An AU coin does NOT have to have luster but the lack of luster will keep it at the lower end of the AU scale, i.e. AU-50/53. Typically, the higher AU grades of 55/58 are reserved for coins showing luster.

Also, just because a coin is brown doesn't imply that it doesn't have luster. Toning has no effect on luster, it's still there under the toning on an MS or high AU coin.