The Number One Dime is the first coin ever earned by Scrooge.
History
When Scrooge was ten, his father gave him a shoeshine kit for his birthday. He then went out to make some money with it, and shined the boots of a ditchdigger. When he finished, he passed out from exhaustion, and when he woke up, he found the first coin he had ever earned in his hand. But when he noticed that it was an American dime, he decided that he would keep it, as a reminder that there would always be sharpies to cheat him.