of the Spanish and Spanish American scribal abbreviation "ps" for pesos. A study of late 18th- and early 19th-century manuscripts shows that the s gradually came to be written over the p, developing into a close equivalent to the "$" mark. However, there are documents showing the common use of the two-stroke version in Portugal already by 1775. Another hypothesis derives the sign from a depiction of the Pillars of Hercules, a classical symbol for two sides of the Strait of Gibraltar, with a ribbon wrapped around both each pillar (or both pillars) in the form of an "S". This device is common support element of the Spanish coat of arms, and appeared on the most common real de ocho coins circulating at the time in the Americas and Europe; namely, those minted at the Potosí mint in Bolivia, which operated from 1573 to 1825. Indeed, one of the names used for Spanish dollars in Qing Dynasty China was . A variant of the above theory claims that the sign comes from the mark of the mint at Potosí, where a large portion of the Spanish Empire's silver was mined, also featured on those coin, which consisted of the letters "P T S I" superimposed. The core of this monogram is a (single-stroked) "$" sign. Yet another hypothesis notes that the English word "dollar" for the Spanish piece of eight originally came (through Dutch daalder) from Joachimsthaler or thaler, a similar large German silver coin which was widely used in Europe. It is therefore conjectured that the dollar sign derived from a symbol consisting of a superimposing S and I or J that was used to denote the German silver coin. Such symbol appears in the 1686 edition of An Introduction to Merchants' Accounts by John Collins. Alternatively, the symbol could have come from a snake and cross emblem on the thaler coins. Less likely theories The following theories seem to have been discredited or contradicted by documentary evidence: Some historians have attributed the symbol to Oliver Pollock, a wealthy Irish trader and early supporter of the American Revolution, who used the abbreviation "ps", sometimes run together, in a letter dated 1778. In 1937, historian James Alton James claimed that the symbol with two strokes was an adapted design of patriot Robert Morris in 1778, in letters written to Pollock. In 1939, H. M. Larson suggested that the sign could