While 1940 proof Mercury dimes are scarce, they are not so to the same degree of rarity as the first proof issues debuting for the series in 1936. About 10,000 examples are known to survive, and most of those are in the PR64-PR67 range. Examples grading above PR67 are extremely rare, and virtually none are known with any substantive cameo frosting. Be wary of any cameo effect evident, as this is most likely doctored.