What do the two lines on the dollar sign mean? But wait, what other currency also uses the $

Check out the number four key on your keyboard. Stamped above it is one of the most powerful symbols in the world: the almighty dollar sign. But the symbol doesn’t just mark the U.S. currency. Originally — and to this day— the emblem also represents the peso. Several Spanish-speaking countries consider it their own. Peso literally means “weight” in Spanish. The origin of the dollar (or peso) sign is uncertain. However, the reigning theory is that
it comes from the Spanish coat of arms, which was engraved on Spanish colonial silver coins, called Real de a Ocho, or “piece of eight.”

 

On the coin, there were two columns, which represented the Pillars of Hercules, and an “S” shaped ribbon around them. Also represented on the coin was the motto plus ultra, which is Latin for “further beyond.” This was added after Christopher Columbus’ voyage to the Americas. The symbol first cropped up in business correspondence between British North America and Mexico in the 1770s. In 1785, the U.S. adopted the currency of Spanish-Mexico. At that time, the dollar sign and the word “dollar” gained widespread use.
Here’s a piece of trivia to impress coin enthusiasts: The dollar symbol did not appear on U.S. currency until the $1 coin that was issued in 2007.