The 1955 and 1956 Melbourne Mint collector proof coins are notable for having two distinct strike types, each with its own mintage figures. The Melbourne Mint officially distinguished these strikes as Proof and Specimen, but in the collector market, they are more commonly known as satin proofs and mirror proofs, respectively.
The mirror proofs, or specimen strikes, feature a finish reminiscent of earlier collector proofs from 1934 and 1938. In contrast, the satin proofs, or proof strikes, resemble the finish of Melbourne Mint proof coins from 1957 onward. The exact reason for producing two different strike types is unclear, but evidence suggests that satin proofs were likely intended for export. American coin dealers had expressed dissatisfaction with the 1934 and 1938 specimens, so a new, more refined finish may have been developed to meet foreign demand. Supporting this theory, most satin proofs can be traced to the United States, while mirror proofs tend to surface in Australia.
Earlier research mistakenly identified the satin proofs as specimens and the mirror proofs as proofs. This misclassification arose because satin proofs bear a closer resemblance to the currency coins, leading some to assume they were the specimen coins. In fact, the opposite is true: the Melbourne Mint's records confirm that mirror proofs are the specimen coins, while satin proofs are designated as proof coins. This aligns with the mint's prior naming conventions, where the 1934 and 1938 collector proofs were also labelled as specimen coins.
Today, both types of 1955 and 1956 proof coins, along with the 1934 and 1938 issues, are collected as proof coins. Within this group, scarcity varies: the 1955 satin proofs are significantly rarer than the mirror proofs, whereas the 1956 mirror proofs are scarcer than their satin proof counterparts.
Many collectors strive to acquire both strike types for a complete set. Satin proofs are often preferred for their consistency with later-year proofs, while mirror proofs stand out with their distinctive finish, differing from both later proofs and the regular currency issue. Including both in a collection not only enhances completeness but also showcases the fascinating variety of finishes produced by the Melbourne Mint.