These proof coins possess beautiful, heavily frosted, snow white devices which contrast with their deeply mirrored fields. They take their name from the cameos that are used in jewelry. Proof coins that don't have these frosted devices are called brilliant proof. The US mint lost the secret to striking these cameo proofs at the end of the 19th century. Between then and 1970 these coins were very rarely struck. Only prefect blanks struck from perfectly polished dies show these features. All proofs since the '70s have been cameo, since the mint figured out how to do it once again. Collectors pay large amounts depending on the contrast involved. They class these coins as Cameo or Deep Cameo depending on the contrast. Cameo & Brilliant Proof Coinage of the 1950 to 1970 Era by Rick Tomaska in the definitive book on the subject.