Begining in 1865 and running through 1869, the U.S. Mint produced a number of pattern 5 Cents pieces in contemplation of replacing the shiled design on the regular issue "Nickels." A large majority of the coins feature a head of Liberty in an enlarged and modified version of the head seen on the regular-issue Three-Cents Nickel. Based on this connection, James B. Longacre gets credit for the design. Mint engravers produced a variety of different reverse designs to mate with this obverse, but adopted none of them for regular use.
Judd-684 features the modified Liberty Head design with a reverse used in 1868 on Judd-631. Ironically, the reverse of this variety is the same "CENTS"-less type that caused so many problems years later on the 1883 No CENTS Nickel.
Judd-684 is very common as far as pattern coins go and can be found in PR64 or PR65 condition with relative ease. Cameo Proof examples appear to be in the minority, and they represent approximately twenty-five percent of the known population.