Pillars of Hercules.

Hercules is credited with founding many cities in Spain and Portugal (eg Seville & Lisbon).

The symbol most associated with him is two pillars, a ribbon and the words PLVS VLTRA, meaning further beyond, reflecting the exploits of the early Spanish explorers in sailing beyond the edge of the earth, as it was known.

The two pillars and the ribbon became the $ sign as it was on early Spanish currency.
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