Although listed as a regular dies trial piece in copper, it is more likely that this was deliberately struck for sale to collectors.
According to Heritage's 4/13 Newman auction description: "Our research indicates two reverse dies were used to strike Judd-549, creating two die varieties for the issue. This coin represents the variety we have designated Reverse A, with the N in IN placed high and the G in GOD placed low in relation to the other devices. Many of the reverse stars show evidence of recutting on this variety. Reverse B was employed on the coin illustrated in the Tree Many Feathers Collection (Bowers and Merena, 9/2001), lot 185, with the letters in the motto arranged in a smooth arc, and no recutting of the stars. Reverse A was also used on Judd-453 in 1865, and on some of the double eagle proof coins in 1866 and 1867. This indicates that the issue must have been struck at some time close to the purported 1866 date and was not a restrike from later years."
StacksBowers in their January 2010 sale believe that what is defined as reverse B here is actually the same as reverse A with the N in IN recut lower. Jacob Lipson from Heritage reports that reverse B was used on regular 1866 circulation strikes including lot 5537 in Heritage 1/14 and also lot 4405 in Heritage 4/18 sales and thus there were 2 reverse dies as one without the recutting was used on regular 1866 and 1867 proofs.
Below are images of the 2 reverses dies.
There are 4 confirmed examples as follows:
1) Newman-EPNNES, Heritage 4/13 - NGC65RB, with reverse of 1865 illustrated above.
2) Stacks 1/06, Simpson-Heritage 8/10 - NGC61 gilt, with reverse of 1865.
3) Stacks 1/10 - NGC62 gilt, with reverse B.
4) Ruby-Superior 2/74, Stacks 1977 FPL, B/M 11/01, Superior 1/03 as NGC63, Simpson-Heritage 2/21 - PCGS63 gilt, with reverse B.
Judd lists one in the Dr. Michal collection (#2?) which may be another or among the last 3.
Photo is of the Eric Newman example courtesy of Heritage.