The 1916-D is the rarest with a mintage of only 264,000 coins.
The 1894-S dime is considered the rarest Mercury dime, with only 24 known to exist. This coin is highly sought after by collectors and can fetch a high price at auctions.
If it's a U.S. dime with a date of 1944, it's a Mercury dime.
The first MERCURY dime was struck in 1916
The Mercury Dime
The Winged Liberty Head Dime also known as the Mercury Dime was minted from 1916-1946.
The U.S. Mint did not issue a Mercury Dime in 1910.
The Winged Liberty, or Mercury Dime. Most people call it the Mercury Dime, but its real name is the Winged Liberty dime.
Do a Google image search for "Mercury Dime" and you will see the photo of the dime.
The 1874-CC Liberty Seated Dime is considered one of the rarest and most coveted silver dimes in American numismatics. It was minted in Carson City, Nevada, and only a small number of specimens are known to exist, making it highly sought after by collectors.
That's off by about 65 years. Mercury dimes were minted from 1916 to 1945. A dime from 1853 would be called a Liberty dime or Liberty Seated dime.
That would be the 1916-D with a mintage of 264,000. However, the 1941/1942 overstrike error with an unknown mintage is also in demand by collectors. More information can be found at this website : http://coins.about.com/od/coinvalues/qt/mercury_keys.htm
A mercury dime has a face of a personification of liberty on it with a winged helmet. They are called mercury dimes because it looks like Mercury from mythology.