David Hall: Like the 1919 and 1919-S, the 1919-D is rare in all circulated grades and very rare in high grades. It is even rarer still in mint state and in Gem condition it is the rarest of all Walking Liberty half dollars. There are just a dozen or so MS65 examples known and anything higher than MS65 is almost unknown. This is a rare coin in all grades and a major 20th century condition rarity in Gem condition.
Strike is a major problem with this issue. Most 1919-D half dollars are very weakly struck thru the central devices, with little if any hand detail on the obverse, and often with weak eagle's breast feathers on the reverse. The lack of striking detail is the major reason Gems are so rare (couple with the overall rarity of the issue in mint state.) Luster is also often a problem and there are some mint state examples with unattractive toning. In short, finding a pleasing mint state example of this issue is very difficult.