20 Centavos (1983-1984), SUBJECT: OLMEC CULTURE. OBVERSE: NATIONAL ARMS, EAGLE LEFT. MASK 3/4 RIGHT, VALUE BELOW. The Olmec were an ancient Pre-Columbian people living in the tropical lowlands of south-central Mexico.The Olmec flourished during the Formative (or Preclassic) period, dating from 1200 BCE to about 400 BCE.