Left Facing Portraits

With ancient coins, left facing portraits are not inherently more valuable than right facing, however for some issues the left facing version is a rarity that specialists will pay more for. Left facing Roman imperial female portraits are particularly rare.

For Roman republican coins left/right portrait is not a way to tell price. Here's the first left facing portrait of Roman. This coin from 137 BC is a relatively common coin and is one of the least expensive RR denarii you can buy.  There is some speculation that the norm-breaking, left-facing portrait was an intentional message of "facing the other way".

Other firsts for this coin:

• First appearance of Apollo: prior to this, reverse imagery was dominated by martial or state deities like the Dioscuri (Castor and Pollux), Jupiter, or Victory in a chariot. 

• Mark of Value: traditionally, the mark of value X (indicating 10 asses) was placed behind the head of Roma. On this issue, it is placed below the chin (to the front), a deliberate rearrangement of the standard obverse field.

• Legend Arrangement: The placement of the inscriptions was inverted compared to standard practice. The moneyer’s name (normally on the reverse) appears partially on the obverse (TAMPIL), and the ROMA legend (typically in the exergue on the reverse) is shifted and paired with the moneyer’s name (M. BAEBI Q.F.) in a non-standard configuration for the era.

137 BC was a period of political disruption in the Roman Republic (there were a lot of periods of political disruption in the last 150 years of the Republic), perhaps this inspired some norm-breaking at the mint. 

• Lex Cassia Tabellaria: this law was proposed by the tribune Lucius Cassius Longinus Ravilla and introduced the secret ballot for non-capital trials (judgments by the people), stripping the aristocracy (Optimates) of their ability to intimidate voters and influence outcomes openly. Speculation: The shift in the coin's design is frequently interpreted as a visual metaphor for this shift in political power.

• The Crisis at Numantia: the Roman consul C. Hostilius Mancinus suffered a humiliating defeat in Spain against the Numantines and was forced to sign a shameful peace treaty to save his army (which the Senate later repudiated). Speculation: The introduction of Apollo (a god associated with healing and prophecy, but also plague and purification) might have been an appeal for divine intervention following this military and moral disaster

Although it is tempting to see "left" and "right" as "liberal" and "conservative" - the Romans would not have made this association.  Our modern orientation of the political spectrum comes from the French National Assembly in 1789: 

- le côté droit (right side): the more conservative supporters of the King and the traditional institutions sat to the right of the President of the Assembly. Sitting at the right hand of the King was a traditional place of prestige in European court culture.

- le côté gauche (left side): supporters of the revolution: commoners, anti-monarchists, and radicals gathered to the left.

These terms surged in the American vocabulary in the 1920s (supported by the Google Ngram data) with a sharp rise in the usage of "left-wing" and "right-wing" in American English that coincides with the Russian Revolution (1917), when Americans needed language to describe the rise of European Communism ("the Left") and Fascism ("the Right").