These were issued in sets along with the 3 cent J618-J620/P687-P689 and 5 cent J633-J634/P704-P706. To view the set, click here.
Obverse die varieties exist for this design. Pollock describes both a high date and centered date for these in nickel J608/P673 as shown in the illustration below with photos courtesy of Heritage.
The first image is of the high date variety which also has the bottom of the Y in Liberty virtually touching Liberty's hair. On the second image, the centered date variety, the Y in Liberty is further from the hair.
The Bass sale had examples from 3 different obverse dies. Several dozen are known.
Less than a half dozen are confirmed in copper of J609/P674. The examples seen by us have been the high date variety.
An incomplete reverse die trial, JA1868-1/P3341 is also known.