Origin of money symbols

What is the origin of the $ sign? Also, what is the origin of the pound sterling sign?

While I’m sure many people will assume that the $ originally came from a merging of U and S (as in the US), but I think the symbol actually goes back to the 1400’s, prior to the revolutionary war. IIRC there is a linkage to the Spanish Dabloon (SP??)

The sterling symbol £ is supposed to look like an ornate capital L with a crossbar or two. The Latin for pound is libra. Pre-decimalisation we also used s for shilling and d for penny (= Latin solidus and denarius).

What does the S in the dollar sign represent?