Obverse: identify the front

The official Banco de México photograph shows the Mexican national arms, with an eagle, snake and cactus, under ESTADOS UNIDOS MEXICANOS. Compare the complete arms and the opposite face together. The national emblem also appears on other denominations and alloys; it cannot establish metal content by itself.

Reverse: identify the back

The Aztec Sunstone fills the center of the reverse. VEINTE PESOS identifies the denomination below, and 15 Gr. ORO PURO states a nominal fine-gold amount rather than gross coin weight. The official reference carries 1959. This calendar-stone design distinguishes the Azteca from the portrait designs on smaller gold pesos.

History and purpose

Banco de México identifies 1917 as the initial Azteca issue and relates it to the specifications of the 1905 monetary reform. The Sunstone gives the coin its common Azteca name. An earlier .875 twenty-peso gold standard is a separate identity with much larger gross and fine weight.

How to identify this variant

Confirm the Sunstone and VEINTE PESOS, then compare 27.5 mm nominal diameter and 16.6666 g gross mass. The reference identifies a lettered edge for this type; obtain a rim photograph because the face images do not document it. The older .875 twenty-peso standard instead weighs 33.84 g and contains 0.9519 reference fine gold troy ounce.

Understanding its metal content

Three correctly identified matching coins total 1.4466 fine gold troy ounces using the reference’s reported AGW. Gross mass includes alloy metal. A separate mass-times-fineness calculation uses the displayed 16.6666 g and .900 inputs; its rounding can differ from reported AGW. Neither calculation measures wear or tests an individual coin, and an uncertain or differently specified piece should not be included.

Dates, varieties and composition changes

The matching reference date list is 1917–1921 and 1959. Its catalogued overdates include 1920/10, 1921/10 and 1921/11. Later restrikes commonly preserve 1959; the reference also records matte restrikes in 1996. The Sunstone, date and overdate details must be examined together, rather than filling the long intervening gap with assumed issues.

Melt value versus collector value

Keep the actual date, any overdate detail, finish, packaging and ownership records with the coin. A documented original issue and a later retained-date restrike can require different collector assessments despite a shared metal standard. Neither the nominal gold amount nor an attractive reference photograph supplies a grade or guarantees a premium. Preserve the existing surfaces for examination.

Authenticity and condition

Photograph both faces and the complete rim in good light without polishing or scratching the coin. Compare the denomination, date, design and nominal dimensions, and keep any holder or certificate associated with its actual specimen. A correct-looking face or plausible mass is only an identification check. Leave an uncertain piece outside the count until its identity and metal are examined.

Selling this coin

Sort 20-peso coins by the exact design and composition before entering quantities. Include clear face and rim photographs, the visible date and any finish or restrike evidence with the existing appraisal request. Older standards, mounted coins and pieces with uncertain identity need individual review. The reference calculation supplies a metal quantity, not a promised purchase price for an unseen coin.

Sources and calculation methodology

The reference’s owner-selected world gold melt row controls 16.6666 g gross, .900 fineness and 0.4822 fine gold troy ounce. Banco de México displays 0.48227 fine ounce and supplies the 27.5 mm diameter. These published amounts have different rounding; the issuer display does not silently replace the selected reference. The exact the reference type page displays 0.4823 AGW, distinct from its melt-table display; this difference is disclosed rather than conflated. The reference’s matching dated type and issuer references are linked separately. Dates describe confirmed face issues and explicitly documented exceptions, not continuous production between endpoints. Genuine issuer photographs are attributed and retain their original dimensions; small reference images do not certify every date or finish. Market pricing remains unavailable until a live provider is approved, so a missing dollar value is not displayed as zero.

Common questions

References

• NGC: world gold melt specifications — identity 20 peso .900 standard; weight 16.6666 g; fineness .900; AGW 0.4822 (checked 2026-10-10)
• NGC: KM478 dates, design and restrikes — identity; dates 1917–1921, 1959; design; restrikes; mass; purity; type AGW (checked 2026-10-10)
• Banco de México: Centenario gold family — identity; diameter 27.5 mm; .900 fineness; fine ounce display 0.48227; design and official images (checked 2026-10-10)

Issue-year references

• NGC: world gold melt specifications
• NGC: KM478 dates, design and restrikes
• Banco de México: Centenario gold family

Content maintained by CashForCoins. Last substantive record update: 2026-10-11. Report a specification or attribution issue through our contact page.

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Photo credits and rights on the linked coin profile.

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Photo credits and rights on the linked coin profile.

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