The custom of using Mercury dimes in hoodoo is well known, to the point that some folks even say that the Mercury dime is the most traditional thing to use for rites like buying grave dirt.
The Mercury dime was produced from 1916 to 1945, but dimes have been produced in the US since 1792. Until 1965, it was the smallest denomination of silver coin and so was popular for use in folk magic, where silver is generally held to be a valuable ingredient for removing jinxes and protecting from harm.
Data indicates tht the tradition of using silver dimes in hoodoo goes back at least to the early 19th century. Archaeologists have found drilled dimes -- such as one uses for making a protective jewelry charm -- in the remains of old slave quarters. Before the Mercury dime, here were some of the other dimes available:
The "Draped Bust" dime, 1796 - 1807.
"Capped Bust" dime, 1809 - 1837.
"Seated Liberty" dime, 1837 - 1891.