What was the reason that a letter 'S' with a vertical stroke down, came to become the symbol of the Dollar?

Question

'$'
what's the history of this symbol?

Answer 1

My dad was taught (way back in 1917) that the letter U and the letter S were super-imposed over one another, which made it an S with 2 strokes to it. (the U part), With the bottom of the U overlapping the bottom of the S - it looks like a U with 2 straight strokes. (try it yourself and see) And I was taught the exact same thing in the early '50's.

Unit of Silver
From 'US'
That $ is a monogram of U and S, which was used as a mark on money bags issued by the United States Mint. The letters U and S superimposed resemble the historical double stroke "$" sign: the bottom of the 'U' disappears into the bottom curve of the 'S', leaving two vertical lines. This double stroke dollar sign has been used to refer to US Currency. Thus, the one stroke design may have been modified to the double stroke design to represent United States currency.

The dollar symbol was in use in colonial times before the American Revolution. Prices were often quoted in units of silver, as the Spanish "piece of eight" was in common use for payment of goods and services. When a price was quoted the capital 'S' was used to indicate silver with a capital 'U' written on top to indicate units. Eventually, the capital 'U' was replaced by double vertical hash marks.
http://en.wikipedia.org/wiki/Dollar_sign#From_.27US.27

The United States Abbreviation Theory
One of the most popular theories is that the dollar sign is derived from the initials of the United States. If you superimpose a capital "U" on a capital "S" then drop the lower part of the "U", what you end up with is a version of the dollar symbol with two strokes. This theory was endorsed by the American libertarian philosopher and staunch defender of capitalism, Ayn Rand, in her novel Atlas Shrugged. Chapter 10 is entitled the Sign of the Dollar. Rand claimed the dollar sign was the symbol not only of the currency, but also the nation, a free economy, and a free mind.
http://www.ex.ac.uk/~RDavies/arian/dollar.html

Answer 2

It comes from the old Spanish sign for the "Real" which was the letter "S" struck through with two columns each representing the 'Pillars of Hercules'.

Answer 3

its something about that its made out of a U and an S, but i dont get it