PCGS has emailed out the inaugural issue of the PCGS eCollector for 2009, Collectors Club members should find it in their in-boxes. This gem is from Vol. 2 No. 14:
Question: What does “cameo” mean, as in cameo Proof? Where are these listed? Is a cameo Proof better than a non-cameo Proof? I am not able to put my finger on much information. Can you help?
Answer: The term cameo with regard to Proofs refers to a Proof coin on which the main design, most notably the portrait or central figure, has a frosted or lustrous finish, while the fields or flat areas are deeply mirrorlike. Just about all of the copper, nickel, silver, and gold Proof coins made at the Philadelphia Mint from the early days, through the time of general availability of Proofs to the public (1858), down to 1902, are cameo Proofs. In 1902-3, someone at the Mint began polishing the deep recesses in the Proof dies, and Miss Liberty on some Proofs of 1902, most all of 1903, and some of later dates have “polished” rather than cameo portraits. Most copper Proofs 1905-1909 (Indian), nickel Proofs 1905-1912), silver Proofs 1905-1915, and Liberty Head gold Proofs 1905-1907 revert to the cameo style. It was discovered that adding the word cameo to a description of, for example, a Proof half dollar of the 1890s, would increase its marketability, never mind that almost all Proofs are normally this way. One thing led to another, and today cameo is a popular adjective, including on some of the more recent holders. Fast forward to 1950, when Proof coins were struck for collectors, after a hiatus since 1942. From 1950 onward, Proof die preparation was apt to be erratic, as demand was tremendous and vast quantities of Proofs were struck. Thus, rather than being prepared by a handful of specialists, Proof dies were processed by more employees at the Mint. Some employees polished the interior of the portrait and others left well enough alone (an unpolished die = a lustrous or cameo portrait in most instances). Thus, among Proofs from 1950 onward there are some notable differences, “polished” vs. “cameo” portraits on some series, such as Franklin half dollars 1950-1963. Such are quite popular to collect and study. Among such later coins the addition of “cameo” to a description has some real meaning.
–Q. David Bowers, Bowers and Merena Galleries