What is the value of a 1965 D quarter?

Answer 1

No such coin exists. In 1965 the US mint switched to copper-nickel coins for the dime and quarter (and 40% silver for the half dollar) from the previous 90% silver standard. In order to force the new coins to circulate rather than be collected, the US mint stopped placing mintmarks on coins from 1965 until 1967 and mintmarks were resumed in 1968. So no 1965 quarter should have a D mintmark. You need to post more information. The only way that such a coin could exist is if its a "D" mintmark on the reverse that is paired with a 1965 obverse die, in which case the coin would be a very rare mule error. But in reality, you either don't have a mintmark on your 1965 coin or you got the year wrong.