It seems that for transition years, there are a lot of mistakes where the wrong die or planchet are used. For example, a 1959 Lincoln Memorial penny with a Wheat die reverse. Could it be possible that a 1965 nickel with a D mint mark on the back exists? Maybe other error examples exist, say, a 1946 PDS nickel with a large war nickel mint mark on the reverse. Maybe a 1946 PDS nickel on a 35% silver planchet (would probably have to weigh them, though I'm sure patina would form). Are these already known to exist, or is it at least possible? Probably unlikely and if found at the Mint, intentionally destroyed. But, it's still possible... right?
Its possible. If your planning on buying one you found on ebay dont spend too much. I thought I saw one too only it was what looked like a 1942 s on the back side which only one is known.But deffinetly possible.
There are 1946 nickels known on 35% silver planchets but as far as I know there has never been a 1965 dated US coin found with a mintmark.
I know of no MM 1965 coins either. I suppose anything is possible.. I am told that if Pigs had wings they could fly. : )