This is an obverse die trial of just the portrait, in white metal or lead, of the design used on 1859 half dollar patterns like J237-J238/P293-P294 which was supposedly created by Longacre. Your editor, Saul Teichman, has always questioned whether this was designed by Longacre or Paquet as the 1859 half dollar patterns used Paquet's punches in the legend "United States of America".
It is considered a dollar pattern because of the size and relief of the portrait.
Only 3 are known and all 3 are illustrated. In order they are:
1) Auction 80 lot 1864
2) Bowers and Merena's 11/85 Kosoff sale lot 1148, Goldberg 1/04 - PCGS62
3) Bowers and Merena's 11/87 Saunders sale lot 485, Heritage 1/08, Heritage 6/08, Heritage 4/12, Scotsman 10/13 - PCGS61.
Click on the thumbnail image to enlarge.
Photos are scans from the 3 sales listed above.