Per the "Encyclopedia Of U.S. Gold Coins 1795-1933" by Garrett and Guth, "The year 1840 is the first year of issue for the Liberty Head quarter eagle design by Christian Gobrecht. Today this date is quite popular for that reason. Surprisingly, these coins were not saved in significant quantities at the time of issue... Most coins seen are poorly struck in the center, with light die breaks sometimes encountered."

The strike is also noted by David Akers in his "United States Gold Coins - An Analysis Of Auction Records - Volume II - Quarter Eagles". He states, "Always flatly struck on the head of Liberty, the stars, and on the eagle. Much more rare than the standard references and even the low mintage would indicate, particularly in grades above EF... Very underrated."

Walter Breen's monograph "New Varieties Of $1, $2.50 and $5.00 United States Gold", suggests the "Broken die state is very rare."

What has not been detailed by any of the authors is that the "broken die state" reverse coins also have a different obverse. The date is in a slightly different location (the 1 is left of center of a dentil versus right) and the 18 is thicker than the normal date. Also the 40 in the date is re-punched with the initial punch high and corrected lower. This can be seen between the crosslet and serif in the 4 and in the inner lower portion of the 0. Reference, PCGS s/n 83921274 (MS63+) and 37305318 (MS62).