Approximately 75 K-6 slugs exist in private hands, around ten of which grade mint state. The K-6 obverse die is known to exhibit die rust in later states. The 887 Obverse die is paired with two reverse dies, and it is the reverse die that determines whether an 1851 Humbert 887-Thousandths $50 is a K-6 or K-7. The K-6 reverse die has a large “target” at its center and has outer engine turning that often extends beyond the edge of the coin. Two were found on the S.S. Central America. A pair of Kagin-6 slugs are known in proof format. The first of these was owned by Augustus Humbert. The second was sent to the U.S. Mint, and is now in the collection of the Smithsonian Institution.