Diagnostic Controls & Presets Extreme Mechanical Mint Error • $1,000–$8,000+ Value
Diagnostic Forensic Readings
Forensic Attribution Diagnostic
Real-time metallurgical and die variety cross-examination verified against certified populations.
Technical Breakdown: Physics, Metallurgy & Die Diagnostics
Feeder Finger Mechanical Dynamics
Modern high-speed coining presses (such as the Schuler press, operating at up to 750 coins per minute) utilize automated reciprocating feeder fingers to slide blank planchets into the collar die:
If the feeder mechanism mistimes, the dies slam shut directly on the protruding feeder finger tip. The sheer force shears off the finger segment, stamping high-relief coin designs directly onto the aluminum prong.
Struck Through vs Struck On Differentiation
Numismatic authenticators distinguish two major error sub-classes:
Feeder fingers that are struck directly without a coin planchet are classified as 'Struck on Feeder Finger' and represent some of the most dramatic, sculptural mint errors in existence.
Documented Benchmark Auction Records
Heritage Auctions Error Coin Signature Session. Intact 2.5-inch aluminum feeder finger tip stamped with crisp Washington quarter obverse details.
Stack's Bowers Rarities Sale. Extremely rare golden dollar impression on an elongated aluminum feeder prong.
GreatCollections Certified Auction. Sheared rectangular feeder fragment displaying Lincoln's portrait and full date.
Frequently Asked Questions
What is a 'Struck on Feeder Finger' mint error?
It is an extreme mechanical mint error where an automated machine arm (the feeder finger that pushes blank coins into the press) gets caught between the dies. The dies smash shut with 100+ tons of pressure, shearing off the tip and stamping the coin design directly onto the aluminum finger.
What does a feeder finger error look like?
Instead of a round coin, it looks like a long, rectangular, or prong-shaped piece of metal with gripping grooves on one end and a sharply detailed coin design stamped into the other end.
What metal are feeder fingers made of?
Most modern feeder fingers are made of aluminum or phosphor bronze. These softer metals are used intentionally so that if a collision occurs, the machine arm deforms rather than destroying the expensive steel dies.
How much are feeder finger coin errors worth?
They are among the most valuable modern mechanical errors, typically selling for $1,500 to $2,500 for Lincoln Cents, and $4,000 to over $8,000 for Quarters, Halves, and Presidential Dollars.
What is a 'Struck Through Scrap' error?
A struck through scrap error occurs when a loose piece of wire, machine turnings, or metal shavings falls into the coining chamber on top of a normal planchet. The foreign scrap is pressed deep into the coin's surface.
Can someone fake this error in a machine shop?
Yes, by squeezing scrap metal or an aluminum rod against a real coin in a hydraulic press. Authentic errors exhibit extreme strike-tonnage metal flow, authentic die polish lines, and no tool shearing marks.
Will PCGS and NGC certify feeder finger errors?
Yes, both PCGS and NGC regularly authenticate and encapsulate genuine struck feeder finger segments in oversized, specialized coin slabs.