The 1964-D Jefferson Nickel has the highest mintage for any Nickel ever struck by the U.S. Mint. This was also the first year in which the mint struck over a billion Nickels for any date.
Compare this to the 1950-D Jefferson Nickel which has a mintage of 2,630,000. Despite the large mintage of the 1964-D Jefferson Nickel, it is also one of the toughest dates in the Jefferson Nickel series to find in high grades. In fact, PCGS has only graded about 35 examples in MS66 with none higher. And with Full Steps, it is considered even scarcer with about 5 or so known examples, in MS66 Full Steps with none being finer.
Out of this large mintage for the 1964-D Jefferson Nickel, there are probably some very nice examples in MS66 grade or higher with Full Steps details just waiting to be found.