The San Francisco Mint produced over 9 million Morgan Silver dollar coins in the year 1879. Of these, a small and unknown number of coins were struck using a reverse die from the previous year of 1878. This was likely due to a reverse die cracking on a coin press during production in 1879, and being replaced with a used die unbeknowist of the slightly different features. Several differences can be noted on the reverse compared to a standard 1879 coin, including flatter breast feathers on the eagle, and a parallel top arrow feather. This variety is very popular today among collectors due to its scarcity and history.