Hello newbie. I'm not sure about the 2005 nickel. You can do some research on "sintered planchet" or "improper annealing" errors. I've read a little about that type of error, but have not seen one first hand, so I'm hesitant to dole out advice on that. It could also be a stain or environmental damage.
On the other hand, your 1943 P nickel is a "war nickel," and I do know a little about that. It's a different alloy composition used from 1942-1945 to conserve nickel for the war effort. The alloy has magnesium, silver, and copper -- it is the silver in the coin that causes it to tarnish. This would be my guess for this coin, as many War Nickels exhibit similar coloring.
On the other hand, your 1943 P nickel is a "war nickel," and I do know a little about that. It's a different alloy composition used from 1942-1945 to conserve nickel for the war effort. The alloy has magnesium, silver, and copper -- it is the silver in the coin that causes it to tarnish. This would be my guess for this coin, as many War Nickels exhibit similar coloring.
























