With regard to the origin of the dollar sign, according to Florian Cajori, author of a standard work (I think the title is either "A History of Mathematical Signs" or "A History of Mathematical Notation"), it originated from the abbreviation <ps>, for "pesos." The two vertical lines have their origin in the downstroke of the <p> followed by a parallel upstroke, followed by a squiggle for the bowl of the <p> and the <s>.
Improbable as this might seem, Cajori demonstrates the evolution of the sign, with examples at different stages of the transition from <ps> to <$>. The form with two vertical strokes, therefore, is the original one. S�amas � Br�g�in ----------------
