I see a major inconsistency, which leads me to believe it's a fake. The stars, which are usually not very well struck, and tend to show wear quickly, are beautiful on your coin. Meanwhile the central devices on the obverse and reverse are very worn down. This doesn't make sense, unless it's a fake.
This is also a year when only proofs were made, and even an impaired proof, would have some luster in the fields.
Looking at the 1878 One I have that is a Genuine one and Comparing I'm afraid I also think its a forgery the wear seems very uneven and the Lettering very obscure.