These were issued in sets along with the cent and 5 cent piece. To view the set, click here.
These were struck from two reverse dies as follows as shown at the bottom of this page:
Nickel with short dentils and low wreath on reverse J676/P753 and is the example illustrated above and the first image below. It is fairly common with several dozen known.
Nickel with long dentils and centered wreath on reverse J676/P755 and appears to be far rarer than the first. It is the second example illustrated below.
Copper J677/P756 which appears to be unique and is ex Brenner-1914 ANS exhibit (where described as longer dentilation on reverse), Brand (journal #92500:815a) and has not been seen since Kagin's 5/57 sale.
Note: P754, the first obverse is unconfirmed in copper.
Photos courtesy of Heritage.