Twenty centavos (1905-1984)

These were made in nine basic types
Type 1 - .800
Type 2 – Little .800
Type 3 – Monogram
Type 4 - .720
Type 5 – Pyramid
Type 6 – New Eagle
Type 7 – Restyled Eagle
Type 8 – Madero
Type 9 – Olmec

Type 1 - .800

 These were authorised by the Ley Monetaria of 25 March 1905 and the decree of 5 April 1905.

KM-435 1908 20c (Stack’s-Bowers ANA auction, 4 August 2017, lot 21264)

These were composed of 80% silver and 20% copper, had a diameter of 22 mm and weight of 5 g.

KM-435 1910 20c inverted 1

One kind of variety which shows up from time to time within many denominations in Mexico coinage involves a date digit struck over an inverted digit. In this 20 centavos example, the second “1” in the date is struck over an inverted “1”. The top point of the “1” can easily be seen at the base of the digit on the right side. This particular variety has been recognized by the NGC Variety Plus program and can be seen in their Census, while PCGS has yet to attribute this variety.

Type 2 – Little .800

On 13 November 1918 Venustiano Carranza reduced the silver content of Mexico’s coins. The reason given in his decree^{Diario Oficial, 14 November 1918} were that
(a) as a result of the rise in the global price of silver, the pesos fuertes had long since been driven out from circulation, and the functions of the fractional silver coinage had been hindered by their increasing tendency to disappear;
(b) this was due to unavoidable economic causes, and so the government was unable to prevent the disappearance of the fractional coinage. The remedy was, therefore, to reduce the quantity of pure silver contained in the fractional coin in such a way that there was no inducement to export, recast or simply hide This was all the more acceptable as the fractional coinage had only a representative value, as an auxiliary to the gold coins, that were the basis of the monetary system.
(c) that, since the old silver pesos had disappeared from circulation for some time, there was no longer any reason to consider them as part of the monetary system; and that, since it was desirable to fractional coins worth one peso, it was necessary to demonetize the old silver pesos, thus completing and consolidating the monetary regime established on 25 March 1905, through the country's definitive entry into gold monometallism.

KM-436 1919 20c

These were like Type 1 but 3 mm smaller in diameter. Mintage was 4,155,000 in 1919. 

When Plutarco Calles authorised the new 10c coin in 1925, he also decreed that the silver 10c, 20c, 50c and $1 coins created by the 13 November 1918 law should be legal tender up to the end of 1925^{Diario Oficial, Tomo XXX, Núm. 3, 6 May 1925}.

Type 3 – Monogram

On 7 January 1920 Venustiano Carranza authorised a new 20c coin in bronze^{Diario Oficial, Tomo XIV, Núm. 10, 12 January 1920}

KM-437 1920 20c

These were composed of 95% copper, 2.5% tin and 2.5% zinc, had a diamter of 32.5 mm and weight of 15 g.

Mintage was 4,835,450 in 1920. 

When Plutarco Calles authorised the new 10c coin in 1925, he also decreed that the bronze 10c and 20c coins, created by the 27 October 1919 and 7 January 1920 laws respectively, should be legal tender up to the end of 1925^{Diario Oficial, Tomo XXX, Núm. 3, 6 May 1925}.

However in 1935, when the high price of silver caused the disappearance of silver coins, Mexico again produced these bronze coins, with 20,000,000 pieces dated 1935.

Type 4 - .720

On 27 October 1919 Venustiano Carranza noted that the continuing rise in the price of silver threatened the disappearance of the one-peso, fifty-, twenty-, and ten-centavo coins created by the previous year’s law, and that the government needed to ensure a supply of such coinage to maintain daily commercial transactions, and so issued a new decree, altering the composition of the 20c, 50c and $1 coins and introducing a new bronze 10c piece^{Diario Oficial, 31 October 1919}.

KM-438

These were same as Type 2 but with reduced silver content (72% silver, 28% copper). They had a diameter of 19 mm and a weight of 3.33 g.

KM-438 1926 20c 6 over 5 (Stack’s-Bowers auction, 17 May 2024, lot 34399)
“The top left corner of the "5" can clearly be seen under minimal magnification”

KM-438 20c 1933 repunched 3 over 3

KM-438 20c 1933 repunched 3 over 3

This is a simple digit repunch and can be seen at the base and right side of the digit while the second coin example shows the repunch at the top and right side of the digit. I like to refer to the second variety as the “horned 3” since it looks like a pair of horns on the top bar of the digit. Closer examination of this coin shows signs that the repunch may be something more than a “3” since there appears to be an area of a slight curve possibly from a “2” digit above the top bar of the digit which would make it a 1933/2 overdate if true. More study would be needed to confirm this possibility; therefore, it will be somewhat of a mystery coin although NGC has graded and attributed it as a 1933/3.

Type 5 – Pyramid

With the beginning of World War II, Mexico became a primary supplier of silver to the United States of America. Such strong wartime demand for the metal increased prices and sparked public hoarding and melting of Mexican silver coinage, particularly of the 20 centavos. In addition, the Casa de Moneda found it difficult to strike enough silver coinage to satisfy public demand.

On 3 August 1943 a presidential decree signed by President Manuel Avila Camacho authorized a new bronze 20 centavos. According to Historia del Banco de México: Volume 3 by Eduardo Díaz (2015), the dies for a bronze 20 centavos piece had been made already by engraver Manuel Luna Negrete, assisted by Francisco Rivera Paniagua.

Those dies were rapidly put to use. Production began almost immediately on 19 August 1943 using “all the copper they could get.” The Casa de Moneda was soon producing 400,000 20 centavos a day. Total production in 1943 amounted to 46,350,000 bronze 20 centavos compared to a scant 3,955,000 silver 20 centavos.

KM-439 1945 20c

The reverse features the Pyramid of the Sun at Teotihuacán with the city’s name at the pyramid’s base. Beyond the pyramid are the volcanic mountains Ixtaccíhuatl and Popocatépetl; above, the denominator 20 is divided by a liberty cap and embellished with sun rays with the mintmark below. In the foreground, two varieties of cactus flank the denomination CENTAVOS and the date.

These had a composition of 95% copper, 4% zinc and 1% tin, a diameter of 28.5 mm and weight of 10 g. 

Type 6 – New Eagle

On 13 September 1955 Adolfo Ruiz Cortines issued a decree giving the characteristics of new coins of 1c, 5c, 10c, 20c, 50c $1, $5 and $10^{Diario Oficial, 15 September 1955}.

KM-440 1960 20c

This is like Type 5, but with the eagle redesigned to have stylised leaf-like feathers and very large feet. There is wider spacing between ESTADOS UNIDOS MEXICANOS.

Type 7 – Restyled Eagle

KM-441 1971 20c

This is like Type 6, but with the obverse further redesigned such that all the devices are depicted as raised outlines on a flat surface, rather than fully contoured shapes. 

There is an interesting mule error known for the 1973 issue. The error pairs the 20 centavos reverse (the pyramid side) with an obverse meant for the 1973 copper-nickel peso. The error is not readily apparent. The size difference is negligible; the 20 centavos has a diameter of 28.5 mm while the peso has a diameter of 29 mm.

Under examination, a few key diagnostics give the mule error away. Most notably, the T in ESTADOS on a normal 1973 20 centavos has a top bar that dips down at the ends; the mule has a T with a straight top bar. The A in ESTADOS also varies from thick with legs connected at the bottom on the regular issue versus a thinner, open version on the mule. The I in UNIDOS stands straight on a regular strike; the mule has an I with its top tilted to the left. Lastly, the M in MEXICANOS is wide on a regular example; the M appears narrow and bold on a mule.

Type 8 – Madero

By the early 1970s, the price of copper had risen enough to surpass the face value. In mid-1974, the Casa de Moneda ended production of the bronze 20 centavos in favor of a lighter, smaller copper-nickel version.

KM-442 1977 20c

These were authorised by a decree of 29 December 1973^{Diario Oficial, 31 December 1973}. They were composed of 75$ copper and 25% nickel, had a diameter of 20 mm and weight of 3 g.

Scott Doll's study of this issue can be found here.

Type 9 - Olmec

KM-491 1944 20c

These were authorised by José López Portillo in a decree of 21 December 1981^{Diario Oficial, 28 December 1981}. They were composed of 95% copper and 5% zinc, had a diameter of 20 mm and weight of 3.04 g.  

Mintage was 200,000,000 in 1983 and 180,320,000 in 1984.