Judd 1456 is a copper version of an 1876 Half Dollar. Only two examples are known, both of which were owned by R.E. Cox, whose collection was sold in 1962. Until 1989, the two coins remained together, then went their separate ways. The PCGS PR64RD was last seen in a 2003 auction. Mega-collector Bob Simpson owns the better of the two, a PCGS MS66+RB.
Usually, off-metal variants are called "die trials" (whose purpose was to show how the dies would strike up without using the intended metal, which was usually more valuable -- in this case, silver). However, Saul Teichman (www.uspatterns.com) suspects that these were struck as part of off-metal sets for sale to collectors.