The 1877 half union with the large head obverse struck in copper.
The following 10 examples are confirmed, 4 of which are gilt.
1) Connecticut State Library ex Mitchelson from Stickney sale
2) Dibello-Stacks 5/70, Bass-HWBRF - PCGS66RB
3) Durham Museum ex Byron Reed, illustrated above
4) Farouk, Schermerhorn, Pittman-Akers 10/97, Southern collection, Simpson collection - NGC67RB
5) Woodin, Newcomer, Boyd, Dr Judd, Hughes 7/80, Ivy 8/83, Rajj, Stacks-Bowers 2011 ANA as NGC64BN, Simpson-Heritage 8/21 - PCGS64BN
6) Kagins 83 ANA, Midwest collection - circulated !!
7) Smithsonian ex Chase Manhattan Bank collection, gilt
8) Bosbyshell, Newlin, Garrett-JHU, B/R 3/80, B/R 87 ANA, gilt
9) Stacks Auction 87, Queller-Heritage 1/09 FUN - NGC65 gilt
10) ANR 6/04 as PCGS62, Heritage 10/11 as NGC63, Kagins 4/19 - PCGS63 gilt
From the population reports, it is likely that a couple more exist.
This design is unique in gold J1546/P1719 and is ex Snowden, Haseltine, Nagy, Woodin and is now in the Smithsonian after a furor erupted over its existence.
The circumstances of the return of this and its companion gold piece J1548/P1721 have been shrouded in mystery but correspondence between Woodin's attorney and the mint in the John Ford library have shed some new light on the matter, and, at a minimum, establish that the 2 pieces belonged to Col Snowden.
One of these letters from Woodin's attorney to U.S. Attorney Henry W. Wise on June 7, 1910 is shown below courtesy of George Kolbe.
"Col. Snowden, who had originally purchased these coins from the Director of the Mint in Philadelphia by depositing the bullion value and the charge for pattern pieces to save them from being melted down, in the course of negotiations between himself and Dr. Andrew, Director of the Mints, came to an agreement with the latter over all matters in dispute between them, and proposed to Mr. Woodin to repay him the $20,000 he had paid for these pieces, in order that he might carry out his arrangement with Dr. Andrew. Mr. Woodin after numerous visits to Philadelphia and Washington and conference with Dr. Andrew, both there and in this city, decided to accept this offer, returned the 50ís to Col. Snowden, and I thereupon notified Mr. Pratt, as did Mr. Woodin, that the incident was closed, and we requested a letter from your office confirming the same. In view of the trouble and expense to which Mr. Woodin was put to facilitate Dr. Andrew in the adjustment of a very difficult situation, your letter seems a little unfair, in that it would tend to create the appearance of a record some time in the future that Mr. Woodin had been compelled to give up something of which he was improperly in possession."
It appears that Col Snowden either gave them back to the Mint or the Mint confiscated them from him after the deal mentioned above was completed.
Incomplete obverse and reverse hub trials of this design are also known.
Photo from the Byron Reed Collection; owned by the City of Omaha, Nebraska; on loan to The Durham Museum.