NGC 1851-O liberty head dollar broadstruck, with a large area of planchet visible in the 6 to 11 o'clock areas. We would call the coin a partial collar strike because there is reeding on a good portion of the edge.  

New Orleans Mint gold errors are rare, and very few are known. This is a dramatic example, with good eye-appeal, and would be a desirable coin in any mint error collection.
 

AU58 with just a hint of wear and nice lustrous surfaces.