8 Reales San Luis Potosí 1890: Value Guide

If you inherited an 1890 Mexican 8 Reales from San Luis Potosí, here is the honest answer: it is real silver, and in worn condition it is worth roughly 25 to 45 US dollars, mostly for its metal. A sharp, uncleaned example can bring 100 to 300 dollars or more. This is a common date, not a rarity, so do not expect thousands.

This is the classic Mexican silver piece US collectors call the "cap and rays" 8 Reales (in Spanish, resplandor, meaning "radiance," named for the radiant Phrygian cap on the front). It is the direct descendant of the Spanish colonial "piece of eight," and for most of the 1800s it was the standard trade coin of Mexico.

What you actually have

• Denomination: 8 Reales
• Year: 1890
• Mint: San Luis Potosí (marked with a small "Pi" mintmark, that is the mint letter, not a typo)
• Metal: silver, .903 fine (about 90 percent silver)
• Weight: 27.07 grams
• Diameter: 39 mm
• Edge: reeded
• Catalog reference: KM#377.12

The front (obverse) shows a radiant Phrygian cap over the word LIBERTAD. The back (reverse) shows the Mexican eagle with a snake, standing on a cactus. Because it is nearly 90 percent silver and weighs 27 grams, this coin has a melt value floor: even a beat-up example is worth its silver, which at recent prices runs around 22 to 26 US dollars per coin. It will not go below that.

How much is it worth?

1890 was near the end of the cap-and-rays series, and San Luis Potosí struck these in large numbers. That makes it a common-date coin. Value comes almost entirely from condition, not age.

Condition	What it looks like	Approx. value (USD)
Worn (VG to Fine)	flat cap, smooth eagle, readable date	25 to 45
Nice circulated (VF to XF)	full cap rays, clear eagle feathers	45 to 90
About Uncirculated	light rub, most detail sharp	90 to 200
Uncirculated (MS62+)	full mint luster, no wear	200 to 500+

These are typical retail ranges, not guarantees. A cleaned coin (shiny but with fine scratch lines) sells at the low end no matter how bright it looks. Original, untouched surfaces are what pushes an 8 Reales toward the top figures.

Is it rare?

No, not this date and mint. The cap-and-rays 8 Reales was minted by the tens of millions across many Mexican mints from the 1820s into the 1890s. San Luis Potosí 1890 is a routine issue. Collectors who assemble a full set by mint and assayer will pay a premium for high grade, but the coin itself is not scarce.

What can add value: genuine mint errors (off-center strikes, die rotation, doubled dies). Real, verifiable errors can multiply the price. But most "errors" people post online are post-mint damage: rim dings, corrosion, or scratches, which add nothing. If you think you have a true error, get it reviewed before you assume it is worth more.

How to tell if it's genuine

Counterfeits of Mexican silver 8 Reales exist, both period-made and modern.

1. Weigh it. A jeweler's scale should read close to 27.07 grams. A fake often runs light or heavy.
2. Measure it. Diameter should be 39 mm. Check the edge: it must be reeded (fine vertical grooves), not smooth or lettered.
3. Check the metal sound and look. Real .903 silver has a warm gray tone, not the bright white of nickel or the yellow cast of a base-metal fake.
4. Inspect the strike. Genuine coins show crisp, hand-engraved detail in the cap rays and eagle feathers. Cast fakes look soft, grainy, or have a seam on the edge.
5. Be suspicious of any offer far below silver value. If someone is selling one for less than the melt price, assume it is fake.

For anything valuable or uncertain, third-party grading from NGC or PCGS settles both authenticity and grade, and it raises resale value.

Where to sell it

• A verified coin dealer will appraise and buy on the spot. Bring the coin, let them weigh it in front of you, and get more than one quote if you can.
• A collector marketplace or numismatic forum often gets you a better price than a dealer, because you skip the middleman markup. Photograph the front, back, and edge in good light.
• Avoid dumping it to the first buyer on general social media. Silver coins get lowballed there constantly.

Before you sell, know two numbers: today's silver melt value (your floor) and the condition-based range above (your ceiling). That keeps you from selling a nice example for scrap.

Got one in hand and not sure of the grade? Post clear photos of both sides in the Pesoteca forum and let collectors help you pin down what it is really worth.

In 1890 Porfirio Díaz was in power during the middle years of the Porfiriato. These were the years of the 1889 Paris Universal Exposition with its Mexican pavilion and of the consolidation of the railroad as the backbone of the economy.

The San Luis Potosí mint (Pi) operated from 1827, fed by the mines of Cerro Potosí and Real de Catorce. It closed in 1893 during the centralizing reform of the middle Porfiriato.

Pi pieces enjoy strong regional demand. Late years (1892-1893) are scarcer because of the mint's imminent closure.

For catalog reference, this mint's variety is listed as KM#377.12 in Krause. The piece is silver of .9028 fineness with a reeded edge and a theoretical weight of 27.07 grams. The 1890 San Luis Potosí example belongs to the mint's final operating years (1827-1893) and is identified on the coin by the Pi mint mark.

The collector building the series by mint tends to hunt down Pi examples of the 1890s cycle in lots or peer-to-peer trades, avoiding the middleman resale. It is worth confirming that the piece weighs close to 27 grams (striking tolerance) and measures 39 millimeters in diameter. Pieces resurfacing from local hoards appear periodically on the market and are the best window to obtain a high grade without overpaying.