I just bought a 1856 half eagle and the reverse is rotated by around 15 degrees or so. Since the coin is slabbed (NGC) my guess would be that this is common but I just thought I'd ask the experts.
I don't know about it being so common but it is strange that NGC did not give it a special designation. Very nice coin though.
It is AU DETAILS, improperly cleaned. I paid about $5 over melt for it. Figured it was hard to go too far wrong.
That's not a bad deal it's a very nice eagle. I did look the coin up on PCGS Coin Fact and I cannot find any errors or varities matching this rotation.
I always thought that icoins had to be over 15 degrees rotated to be outside of mint specifications. Great coin, especially at $5 over melt.