Money is explained by this 1947 Coronet film.
It explains the progression of our economic system, beginning with bartering by early humans. Because of specialization, bartering is no longer appropriate and money has emerged. First there were spearheads and other unreliable forms of wealth, which eventually led to the use of silver and gold coins. The mint system is shown as it is explained that the government is the backbone to the value of our money.
Although it shows its age, as a 1940s film, it would spark some interesting discussions on money in any Social Studies class.