1928-D Standing Liberty Quarter
Of similar absolute and strike rarity to the 1919-S, the 1928-D is definitely one of the most underrated issues in the Standing Liberty Quarter series. Only 1.6 million pieces were produced, and less than 1% of that already limited mintage is believed to have been struck with Full Head definition (per J. H. Cline, Standing Liberty Quarters, 2007 edition).
The example to the left was sold by Stack's Bowers Galleries in the August 2012 Philadelphia ANA Auction, where it realized $64,625.