Although described as a regular dies trial piece in nickel, it is more likely that this was deliberately struck for sale to collectors.
About a half dozen are known including 2 in the Smithsonian, one in the Durham Museum and one in Eric Newman's collection. Some of these were apparently struck from business strike dies.
They appear to have been struck on whatever planchets were available. Pollock lists one of the Smithsonian examples at 54.2 grains which is from the same planchet stock used to strike many thin planchet 5 cent nickel patterns of that year. The Byron Reed coin is on an even thinner planchet 39.5 grains as opposed to the 36.6 listing in Pollock.
It is likely that some of these were struck on regular thickness shield nickel planchets. If so, these examples may be mint errors.
An aluminum example J544/P609 was listed as lot 536 in Woodward's 3/1880 sale and a copper piece was listed in an 1869 Cogan sale. Both of these are unconfirmed today and are likely not genuine.
Photo courtesy of Bowers and Merena.