Where Does the Dollar Sign Come From? Marks With Contested Histories

A currency mark serves a specific set of requirements that shape its form. It must be quick to write by hand, which favours simple strokes and is why most are a letter with one or two lines through it. It must be unmistakable at small sizes and in poor printing. It must not be confusable with other marks used in the same documents, particularly numerals and arithmetic signs. It must work alongside numbers without the two running together, which is why a vertical stroke element is so common. And it must be distinguishable from other currencies, which becomes harder as more are created. Those constraints explain the family resemblance between marks invented independently.

Origins vary and some are solid while others are not:

• •The pound mark is a stylised capital L from the Latin word for a pound weight
• •The dollar mark most likely derives from a handwritten abbreviation of pesos, with the S and P merging
• •The competing account deriving it from the Pillars of Hercules on Spanish coins is picturesque and less supported
• •The yen and yuan marks are a Y with strokes, introduced when those currencies were established
• •The euro mark was designed by committee in the 1990s from a Greek letter with two bars
• •The Indian rupee mark was chosen by public competition in 2010 and combines a letter from two scripts

Introducing a symbol is now a deliberate process with technical requirements, which the euro illustrated. A new mark must be added to the international character encoding standard before it can be typed, displayed or transmitted reliably, which requires a formal proposal and takes time, and until that happens the symbol exists only as a picture. Fonts must then be updated to include it, and old software and documents never will be. Keyboards must provide a way to type it. The euro's introduction required all of that and produced a period during which the symbol displayed incorrectly on a great many systems. The Indian competition winner faced the same sequence. A symbol that cannot be typed is not much use, which is a constraint no earlier currency faced.

Placement and spacing follow conventions that differ between languages and are frequently got wrong. English places the symbol before the number with no space, while most continental European conventions place it after with a space, and the same currency is therefore written differently in different countries that use it. The decimal separator is a point in some conventions and a comma in others, with the thousands separator taking whichever the decimal does not, which produces genuine ambiguity in international documents and has caused real errors. Negative amounts are shown with a minus sign, with brackets in accounting convention, or in red. Some currencies are conventionally written with the code rather than a symbol precisely to avoid all of this, which is why financial documents look the way they do.

For anything beyond display, currencies are identified by three-letter codes rather than by symbols, and the reasoning is practical. A standard maintained internationally assigns each currency a code, generally two letters for the country and one for the currency name, which is unambiguous, typeable anywhere and immune to the confusion between several currencies sharing a symbol, since a great many countries use a dollar or a pound of their own. Banking, accounting and trading systems use those codes exclusively. The standard also assigns numeric codes and specifies how many decimal places each currency uses, which matters because several have none and at least one has three, and software assuming two produces errors.

A mark must be quick to write, unmistakable when small and not confusable with numerals, which is why most are a letter crossed by strokes. The dollar sign most likely comes from a merged abbreviation of pesos rather than from anything on a coin. New symbols must be added to the international character standard before they can be typed at all.