This is Morgan's eagle design identical to the one made the prior year J1545/P1718 except for the date.
This design was also made into a half eagle J1577-J1578/P1770-P1771.
2 examples were struck in gold J1577/P1770. Roger Burdette noted the following from a January 12, 1878 Mint archive: "Two eagles and two half eagles, Morganís design, in gold. For directorís office."
Pedigrees for the 2 known eagles are below:
1) Massamore 11/1884 lot 506, Barlcay-Steigerwalt 4/1885 lot 988, Ely-Scott Stamp & Coin 11/1888 lot 114, C.F. Libbie 10/1901 lot 825, Mitchelson, Connecticut State Library
2) Parmelee, V. Brand (journal id #12721) to Horace Brand, Judd, Wilkison, Auction 90, southern collection, Simpson collection - NGC66 and is illustrated above.
Only 3 examples are known in copper J1582/P1775 including 2 in the Smithsonian and a cleaned example in a PCGS62RB holder ex Bowers and Merena 3/2000, Heritage 5/01, Heritage 1/07.
Additional information on these can be found in the article "The 1884 Connection: A History of the 1878 U.S. Gold Patterns" in the November 1981 issue of The Numismatist.
A reverse hub trial showing just the eagle, struck in lead, JA1878-5/P3464 is also known.
Image courtesy of Andy Lustig.