The white is just dust. Coin is in great shape just this weird color. Weight is 5.0. No scratches that show silver underneath. What's going on??
A coin coloring is often referred to as "toning". There is artificial toning (AT) and there is natural toning (NT). Without knowing where the coin has been or what it has been into, it's virtually impossible to say exactly what caused it. Some possibilities are exposure to chemicals or gasses. Maybe it was buried in the ground for a while. Sometimes being in a paper holder can cause toning. Another member had a large silver coin that accidentally got soaked in motor oil. After he wiped it off, it developed a similar brownish color. We will probably never know.
You need to learn more about grading. This coin is in terrible shape. Also, the only nickels that contain any silver are the war nickels, 1942-1945. Chris
Correct! Environmental Damage. Here are many Nickels I have found metal detecting with the same issue.
There is copper in the cupro-nickel the coin is made of. The copper reacted to long term exposure to the elements as you see in my picture above.
Also.. Think about this carfully.. If your Nickel was struck on a Copper Cent Planchet in error it would be the same size, thickness and weight of a Copper Cent.
A US Nickel is 75% Copper and 25% Nickel. The outer clad layers on the Dime, Quarter, and Half also use the same composition. This alloy will turn brown when exposed to a number of environmental factors, especially if it’s been buried. You can see this on @paddyman98 metal detecting finds posted above. It is not an error
The problem is that Jefferson Nickels need to be in GEM grade or better to have any real numismatic value (excluding varieties). This is true going all the way back to the first year of issue in 1938. Your coin is a circulated 1977 with unattractive toning, and is not ever going to be collectible. It’s a spender.