The famous 1861 regular dies trial piece struck in copper without a collar. Pollock noted that the coin has a reeded edge, not a beveled edge as mentioned in the first 7 editions of Judd.
Dr. Judd and/or Walter Breen believed this to be an experimental piece using ideas from Dr. J.T. Barclay to prevent counterfeiting. The coin is very concave which would have made it more difficult for unscrupulous types to drill out the gold and replace it with a less valuable metal.
A collector, Greg B., wrote us about the possibility that this piece may actually be a misstruck example of J289/P347. We quote him below.
"The coin, in my opinion, has been double struck: the first strike was on center, and in the collar. This would account for the perfect and normal reeding. The second strike was a broadstrike, without the collar. This would account not only for the beveled edge, but also for the spread design as seen in the pictures."
Greg also sent us an image of a 1964 Great Britain two shilling piece which was struck as described above and it does have a similar appearance to the double eagle trial.
Pattern author and researcher Roger Burdette, however, found in the National Archives (NARA-CP RG104 Entry 229 Box 3) the following document entitled "List of Pattern, Trial and Experimental Coins Struck in the United States at Philadelphia from 1792 to 1885". Accompanying this listing is a letter written on July 6, 1887 by the Director of the Mint, James P. Kimball and the Mint Superintendent Daniel M Fox to R. A. McClure, Curator of the Cabinet. This listing describes this very piece as "1861. Double Eagle. device same as the regular issue. Obv. Concave, edge bevelled." This listing seems to verify that this is in fact an experimental piece unless it is referring to J190/P3158 instead.
Only one or two are known including the illustrated piece which is ex Woodside, Woodin, Farouk, Judd, Kosoff 2/70, Bowers and Merena 11/85, Heritage 2/86, Superior 9/86, Superior 2/92, ANR 7/05. A second is mentioned as being in the Connecticut State Library; but, if it is there, then I missed it during my visit.
Photo courtesy of American Numismatic Rarities.