Old Mexican Silver Coins

The original piece of eight:
two centuries of real money.

A printable reference to Mexican silver coinage — from Spanish colonial 8 reales (the world's first global trade dollar) through the Caballito peso, the Cuauhtémoc 5 pesos, and the modern Onza Libertad bullion. Three centuries; one metal.

The shortcut to remember 8 reales / 1 peso = ~0.786 troy oz of silver For any pre-1918 Spanish or Mexican 8 reales or 1-peso coin (.903 fineness, 27.07 g). The Spanish "piece of eight" was the global reserve currency for 250 years; this is what it weighed.

Silver Content Reference — Mexico

From Spanish colonial 8 reales (Mexico City Mint, founded 1535 — the oldest mint in the Americas) through modern Libertad bullion. Standard mint specifications.
Mexico City Mint silver was, for centuries, the de facto international currency — circulating from China to the American colonies as "Spanish dollars."
Spot prices used for "Melt": Ag — Cu — From the calculator; live spot will differ.
Coin Years Total wt Composition Silver (ozt) ≈ Fraction Face
Spanish colonial silver — Mexico City Mint, 1772–1821
8 reales (Spanish colonial)
 1772–1821 27.07 g 90.3% Ag · 9.7% Cu 0.7859 ~4/5 oz 8 reales
Mexican Republic silver — 8 reales / 1 peso, .903 fineness
8 reales (Republic)
 1823–1897 27.07 g 90.3% Ag · 9.7% Cu 0.7859 ~4/5 oz 8 reales
1 peso (.903) 1869–1873, 1898–1909 27.07 g 90.3% Ag · 9.7% Cu 0.7859 ~4/5 oz 1 peso
Caballito peso
 1910–1914 27.07 g 90.3% Ag · 9.7% Cu 0.7859 ~4/5 oz 1 peso
50 centavos (.903) 1869–1895 13.54 g 90.3% Ag · 9.7% Cu 0.3930 ~2/5 oz 50¢
25 centavos (.903) 1869–1892 6.77 g 90.3% Ag · 9.7% Cu 0.1965 ~1/5 oz 25¢
Reduced fineness — 1918–1945 transitional pesos
1 peso (.800) 1918–1919 18.13 g 80% Ag · 20% Cu 0.4663 ~1/2 oz 1 peso
1 peso (.720) 1920–1945 16.66 g 72% Ag · 28% Cu 0.3856 ~2/5 oz 1 peso
Modern silver pesos — Cuauhtémoc, Hidalgo, Olympic
5 pesos Cuauhtémoc
 1947–1948 30.00 g 90% Ag · 10% Cu 0.8681 ~7/8 oz 5 pesos
5 pesos Hidalgo
 1951–1954 27.78 g 72% Ag · 28% Cu 0.6429 ~2/3 oz 5 pesos
25 pesos Olympic 1968 22.50 g 72% Ag · 28% Cu 0.5208 ~1/2 oz 25 pesos
Bullion — sterling and pure silver "Onzas"
Onza Troy (1949) 1949 (one year) 33.625 g 92.5% Ag · 7.5% Cu 1.0000 1 oz exact — bullion
Onza Libertad
 1982–present 31.103 g 99.9% Ag 0.9990 1 oz exact — bullion
Pre-1918 silver pesos / 8 reales Any .903 silver Mexican peso or 8-real coin: 1 peso = 0.786 ozt. A roll of 20 ≈ 15.7 ozt.
Cuauhtémoc 5 pesos (1947–48) Largest modern Mexican silver coin: 1 coin = 0.868 ozt. The two-year-only run keeps premiums modest above melt.
Modern Libertad bullion Exactly 1 troy ounce of .999 silver; 1 oz = 31.103 g. Trades at spot + small premium worldwide.
Metal legend — click any badge for details

Why "piece of eight": the Spanish 8-real coin (silver real = a unit of account) was physically divisible into eight pie-slice "bits" — hence "two bits" for a quarter. The 8-real / Mexican peso was the de facto global trade currency from the 1500s through the early 1900s, accepted from Spanish missions in California to the Qing dynasty treasury in Beijing. The US silver dollar weight (26.73 g / .900) was deliberately set close to the Spanish dollar (27.07 g / .903) so the two coins could be used interchangeably.

Caballito peso: the 1910–1914 "horse" (caballito) peso designed by Charles Pillet shows Lady Liberty on horseback — widely considered one of the most beautiful designs ever struck on a Mexican coin. Same weight and silver content as the Republican 8 reales, just rebranded as 1 peso.

Cuauhtémoc & Hidalgo 5 pesos: the 1947–48 Cuauhtémoc 5-peso (30 g, 90% silver — heavier than a US silver dollar) was the largest Mexican silver coin of the 20th century. The 1951–54 Hidalgo 5-peso commemorated Miguel Hidalgo (the priest who launched Mexican independence in 1810); fineness dropped to .720 as silver prices rose.

Onza Libertad: the modern bullion coin (1982–present) shows the Mexican coat of arms on the obverse and the Angel of Independence (Winged Victory) on the reverse. Widely considered one of the most beautiful sovereign-issued bullion coins. .999 fineness, exactly 1 troy ounce — the Mexican answer to the American Silver Eagle and Canadian Maple Leaf.

Coin photos via Wikimedia Commons. Public domain (mint historical) and CC-licensed contributor uploads. Click thumbnails for sources.

Data sources: Casa de Moneda de México specifications · Krause Standard Catalog of World Coins · Bauche Las Monedas de México. Conversions mirrored across this site.