Scrooge McDuck's name for the first dime he ever earned (by shining an incredibly muddy pair of boots in
Glasgow,
Scotland, in the 1870s). He considered it to be the source of all his wealth, although this was disproven on several occasions. The witch
Magica de Spell was also convinced that the dime was a wealth charm, and constantly tried to steal it to melt it down (along with dimes from other rich people) to make a wealth
amulet.
Scrooge kept the dime alternately under a glass case on a pillar in his office in the money bin, or in his pocket. The constant wearing down from being in his pocket for so many years made it very sharp, and it could be (and was) used to cut through rope.