The Valuable 1999 State Quarter Errors (Complete Guide)
The 1999 State Quarters were the inaugural batch of the 50 State Quarters Program, and the U.S. Mint was under intense pressure to produce them at speed. That urgency, combined with experimental alloy testing for the soon-to-launch Sacagawea dollar, produced a surprisingly wide range of mint errors. The varieties below are ordered from most to least financially significant — each has been documented by third-party graders PCGS or NGC.
In 1999, the U.S. Mint was actively testing copper-zinc-manganese-nickel alloys for the upcoming Sacagawea dollar, which would enter circulation in 2000. Because Sacagawea dies were not yet ready, engineers tested the new alloy on available quarter dies. A small number of 1999 State Quarter dies from the Philadelphia Mint were used to strike coins on this experimental "golden" planchet — meaning the coins were an intentional test, not a random accident, though PCGS designates them as errors.
Visually, these coins appear distinctly golden, brassy, or lemon-yellow rather than the standard silver-gray of clad coinage. All five 1999 state designs — Delaware, Pennsylvania, New Jersey, Georgia, and Connecticut — exist on experimental planchets, all bearing the P mint mark. The most reliable authentication test is weight: standard quarters weigh exactly 5.67 grams, while experimental planchet examples weigh between 5.9 and 6.3 grams on a precision scale.
These are the most sought-after 1999 quarters in the entire series. The value cliff is steep — only PCGS-certified examples should be trusted, as gold-plated standard quarters are a documented counterfeit category. All five state designs command four- to five-figure prices when certified. Their historical significance as precursors to the Sacagawea dollar adds a numismatic narrative that drives sustained collector demand.
The Spitting Horse is the most recognized and most searched error variety in the entire State Quarters Program. It occurs on 1999-P Delaware quarters — the very first state quarter ever released — when a crack developed in the reverse die. The die crack runs from the mouth of the horse that Caesar Rodney is riding, downward through the die field toward the "C" in "Caesar," producing a raised ridge of metal on every coin struck from that damaged die.
Visually, the raised line looks exactly like the horse is expelling a stream from its mouth — hence the nickname. To distinguish the genuine die crack from a post-mint scratch, look under a 5× or 10× loupe: the Spitting Horse line is raised (proud of the surface, like a thin wire pressed onto the coin), while a scratch is incuse (sunken below the field). Only 1999-P Delaware quarters can carry this variety — the D mint and proof versions do not.
Despite being the most famous 1999 quarter error, the Spitting Horse adds modest rather than dramatic value: circulated examples trade for $3–$20 above face value depending on how sharp and prominent the crack is. High-grade MS-67 examples certified by PCGS or NGC can exceed $40. The variety's celebrity status makes it a gateway error for new collectors and means even worn specimens are worth pulling from circulation.
Standard clad quarters are a sandwich of three metal layers: an outer 25% nickel layer on each face bonded to a pure copper core. Occasionally, one of the outer nickel layers fails to bond before the blank is punched and struck, leaving that entire face in a reddish-orange copper color. The result is a coin that looks like two different metals — one side silver-gray, the other a warm copper-brown — which even non-collectors immediately notice.
Both 1999-P Georgia and 1999-D Delaware quarters have been documented with this error by numismatic researchers. The missing clad layer affects the entire face (obverse or reverse), not just a patch, distinguishing it from environmental damage or post-mint stripping. Under a loupe, the surface shows the characteristic texture of pure copper rather than the layered appearance of the bonded clad sandwich. The edge of the coin may also reveal the missing layer by showing only copper without the nickel cladding on one side.
Collectors prize missing clad layer errors for their dramatic visual impact — the copper face immediately signals that something went wrong at the mint. Certified examples attract strong interest. Values between $400 and $800 reflect the market for authenticated, uncirculated or lightly circulated specimens; heavily worn examples bring less. As with all error coins, PCGS or NGC certification is strongly recommended before selling.
An off-center strike occurs when the planchet is not properly seated in the collar before the dies close, causing the design to be impressed off to one side and leaving a curved blank crescent on the opposite edge. On 1999 State Quarters, off-center strikes have been documented across both the Philadelphia and Denver mints and across multiple state designs. The degree of shift varies dramatically — from a modest 5% (barely noticeable) to a dramatic 50% or more (where less than half the design is visible).
Value is directly tied to the percentage of off-center shift and to whether the date remains visible. A coin shifted 10–15% off-center brings $20–$100 in circulated grades. At 30–50% off-center, the same coin in uncirculated condition commands $300–$600. Coins shifted 50%+ with the full date visible are the most valuable within this error category — the date visibility confirms the year without doubt. Pieces that lost the date in the shift are less desirable to type collectors.
Off-center strikes on State Quarters are collectible because the state design elements — maps, monuments, and symbols — make the off-centered impression visually striking when the design is partially visible against the blank field. A Delaware Spitting Horse quarter that is also off-center would represent a double error and carry compounded value. Always examine both sides to document which die (obverse or reverse) was responsible for the misalignment.
Doubled die errors occur when the working die receives a second hub impression that is slightly rotated or shifted relative to the first, baking two offset images of the design into the die itself. Every coin struck from that die then shows the doubling permanently. On 1999 State Quarters, DDO varieties have been found across multiple state designs and both Philadelphia and Denver mints, with doubling most commonly appearing in the date, LIBERTY, IN GOD WE TRUST, and Washington's facial features.
The most significant DDO in the 1999 series is the 1999-S Pennsylvania Clad Proof Obverse Doubled Die, listed in the Wexler Doubled Die files. Because it affects a proof coin, the doubling is exceptionally crisp and legible — proof dies are polished and the doubled impression is sharper than on business-strike versions. Minor doubled die varieties also exist on 1999-P and 1999-D Delaware and Pennsylvania quarters, including WDDO-001 and WDDO-002 designations showing doubling in the earlobe area of Washington's portrait.
Values for DDO varieties on 1999 quarters range from $50 for minor doubling on a circulated business strike to over $400 for strong, certified doubling on an uncirculated or proof specimen. The Wexler attribution and PCGS or NGC certification significantly increase realized prices. Collectors should not confuse machine doubling (a flat, shelf-like spread with no depth) — which adds no value — with true hub doubling, which shows a distinct secondary image with full depth.
