Barber's capped Liberty design in gold. This was also made as a half eagle J1575-J1576/P1768-P1769.
Only 2 examples were struck in gold J1579/P1772. Roger Burdette found the following notation in the Mint Archives. "Feb 19, 1878, Two eagles and two half eagles of Barberís design in gold for directorís office."
The 2 pieces have the following pedigrees:
1) Parmelee, V. Brand (journal id #12719) to Horace Brand, Judd, Wilkison, Rothchild-Stacks 10/03, southern collection, Simpson collection - PCGS65, illustrated above courtesy of PCGS, click on the thumbnail to see an enlargement.
2) Massamore 11/1884 lot 506, Barclay-Steigerwalt 4/1885 lot 988, Foster Ely-Scott Stamp and Coin 11/1888 lot 112, Byron Reed, Durham Museum - ICG64, illustrated below.
Photo from the Byron Reed Collection; owned by the City of Omaha, Nebraska; on loan to The Durham Museum.
About a dozen are known in copper J1580/P1773 on both thick and thin planchets including the example illustrated below. Several of these have been gilted.
Photo courtesy of Tangible Asset Galleries.
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.