1955-1971 - 20 Centavos (20C)
In 1955, bronze 50 centavos were introduced, along with smaller 5-peso coins and a new 10-peso coin. In 1957, new 1-peso coins were issued in .100 silver. This series contained 1.6 g of silver per peso. A special 1 peso was minted in 1957 to commemorate Benito Juárez and the constitution of 1857. These were the last silver pesos. The 5-peso coin now weighed 18 grams and was still 0.720 silver; the 10-peso coin weighed 28 grams and was in 0.900 silver.
Between 1960 and 1971, a new coinage was introduced, consisting of brass 1 and 5 centavos, cupro-nickel 10, 25 and 50 centavos, 1, 5 and 10 pesos and silver 25 pesos (only issued 1972). In 1977, silver 100 pesos were issued for circulation. In 1980, smaller 5-peso coins were introduced alongside 20 pesos and (from 1982) 50 pesos in cupro-nickel. Between 1978 and 1982, the sizes of the coins for 20 centavos and above were reduced. Base metal 100, 200, 500, 1000 and 5000-peso coins were introduced between 1984 and 1988.
REF
Weight: 9.93
Diameter: 28.5
Thickness: 2.09
Obverse: 20 CENTAVOS 1944 TEOTIHUACÁN
Reverse: ESTADOS UNIDOS MEXICANOS
Edge: plain
Mint mark: MO (Mexico city, Mexico)
Mintage: 83.650.000
Krause and Mishler Number: KM# 439
1955-1971 - 20 Centavos