Mule Error Coins

Specifications

Denomination: multiple
Series: Mint error types

A mule pairs an obverse and reverse die that were never meant to meet — one side’s design belongs to a completely different coin. They are among the most valuable modern U.S. errors, with 2000-P Sacagawea/quarter mules realizing $100,000–$200,000 at auction, but genuine U.S. mules are vanishingly rare, so authentication is essential.

Classical Numismatic Group, Inc. / Wikimedia Commons (CC BY-SA 3.0)

What it is

In numismatics a mule is a coin or medal struck with obverse and reverse designs not normally seen on the same piece — the name comes from the mule itself, the hybrid offspring of a horse and a donkey, since the coin has two sides intended for different coins. (Wikipedia; accessed 2026-09-17)
It is a striking-stage error: the classic mechanism is a die-room mix-up — the wrong die gets installed in the press, and coins are struck pairing two unrelated designs before anyone notices. (Wikipedia; accessed 2026-09-17)
Mules can be intentional or produced by error; the error kind is highly sought after by collectors, with examples fetching high prices. (Wikipedia; accessed 2026-09-17)
Two-tailed coins are a subtype of same-design mules, struck with two reverse dies — e.g., a two-tailed dime and a two-tailed quarter in the U.S. census. (MinTerrorNews; accessed 2026-09-17)
So-called “handsome” mules pair an identifiable proof die with a business-strike die — their details are noticeably sharper, as on 1958 Franklin half examples. (Wikipedia; accessed 2026-09-17)

How it happens

The wrong die gets installed in the press — a die from a different denomination, series, or year that happened to be nearby in the die room.
Coins are struck pairing two unrelated designs before anyone notices the mix-up.
Once discovered, the dies are pulled and replaced — which is why genuine U.S. mules are vanishingly rare.

How to identify

A true mule shows two complete, properly struck designs from mismatched dies — not one design struck over an already-struck coin (that is a double denomination).
Check that both designs’ eras overlap: a genuine mule’s two dies had to exist at the same mint at the same time.
Weight, diameter, and edge should match the host planchet of the denomination actually struck.
Known mules have published die markers (die cracks, striation patterns); compare a candidate against them.

Real error vs. post-mint damage

Altered “two-headed” novelties and illicitly impressed pieces exist — a claimed mule needs documented die characteristics, not just two designs.
Collectors should be cautious, because pieces can also be created inside the Mint without a coining press (illicit die impressions), whose status as genuine errors is controversial. (error-ref; accessed 2026-09-17)
Because genuine U.S. mules are vanishingly rare, get PCGS/NGC error attribution before paying any premium.

Notable examples

The most famous U.S. mule — the 2000-P coin with a Washington quarter obverse and Sacagawea dollar reverse — is covered in depth in this wiki’s dedicated 2000 mule dollar entry, including its discovery, the Mint’s August 4, 2000 acknowledgment, and the nineteen known examples. (CoinWeek; accessed 2026-09-17)
2014-D Sacagawea dollar obverse / Presidential dollar reverse mule, unique — $70,000 plus buyer’s fee at Heritage’s April 2021 Platinum Night auction. (CoinWeek; accessed 2026-09-17)
2000-D Sacagawea dollar / South Carolina quarter reverse mule. (MinTerrorNews; accessed 2026-09-17)
Cent/dime mules dated 1993-D, 1995, 1999, and 2001-D, plus a two-tailed dime and a two-tailed quarter. (MinTerrorNews; accessed 2026-09-17)
2007 Abigail Adams / Louisa Adams First Spouse medal mule — some 2007 First Spouse medal sets contained Abigail Adams obverses struck with the reverse intended for the Louisa Adams medal; eBay prices reached $925.99 that March. (Coin World, via Wikipedia; accessed 2026-09-17)
Mules are a worldwide phenomenon: in 2014 the Royal Mint confirmed about 38,000 £2 Lunar Horse coins struck with the Britannia obverse and about 17,000 £2 Britannias with the Lunar Horse obverse; in June 2009 a dateless British 20 pence mule from the 2008 redesign entered circulation with an estimated 50,000 to 200,000 released; the Royal Canadian Mint’s 2010 Vancouver Olympic program produced several circulating mules; and a 1967 New Zealand 2 cent coin was issued with the obverse of the Bahamian 5 cent piece. (Wikipedia; accessed 2026-09-17)

What drives value

Severity of the mismatch: the more dramatically unrelated the two designs, the stronger the collector demand.
Confirmed rarity: premiums follow the confirmed population — the famous 2000-P Sacagawea/quarter mules realize $100,000–$200,000 at auction, with an MS67 example reaching $192,000 in 2018. (CoinWeek; accessed 2026-09-17)
Condition: high-grade certified examples draw error, commemorative, and series collectors at once.
Honest floor: because genuine U.S. mules are vanishingly rare, almost any un-certified claimed mule is far more likely to be an altered novelty or an illicit impression than a genuine error — no premium without PCGS/NGC error attribution.