This Half Dime is struck in medal fashion instead of coin fashion. The obverse and reverse instead of being 180* apart are struck with the same die rotation! It is called a 180* error or medal strike.
Rarity and Survival Estimates
Survival
Grades Estimate
All Grades 350
60 or Better 50
65 or Better 6
The Survival Estimate represents an average of one or more experts' opinions as to how many examples survive of a particular coin in three categories: 1) all grades, 2) 60 or better, and 3) 65 or better. These estimates are based on a variety of sources, including population reports, auction appearances, and personal knowledge. Survival estimates include coins that are raw, certified by PCGS, and certified by other grading services.
Ron Guth:
The 1856-O boasts a fairly substantial mintage of 1.1 million pieces
but, because the New Orleans Mint was so far from collectors, the number
of Mint State examples is less than expected. In fact, the 1856-O Half
Dime is valued about the same as the 1855-O With Arrows, which has a
lower mintage and is more in-demand as a type coin. Gem examples of
this date are extremely rare and the best examples reported are a pair
of PCGS 66s.
Don't expect much out of the strike on 1856-O Half Dimes. The
denticles are almost always weak, and the stars and wreath often lack
detail, as well.