Diagnostic Controls & Presets Famous Modern $5,000 Proof Error
Diagnostic Forensic Readings
Forensic Attribution Diagnostic
Real-time metallurgical and die variety cross-examination verified against certified populations.
Technical Breakdown: Physics, Metallurgy & Die Diagnostics
Hub Preparation Anomaly Mechanics
In 1990, master dies and working dies for all denominations were created at Philadelphia. A proof-designated working die failed to receive the 'S' mintmark punch before being sent to San Francisco:
The die was acid-etched and diamond-polished for proof service, then run on a hydraulic press striking specially annealed, copper-plated zinc planchets before the error was caught.
Core Metallurgy & Physical Parameters
Both business strikes and proof strikes for 1990 share identical copper-plated zinc core metallurgy, but differ radically in strike pressure and rim squareness:
Counterfeiters who grind off the 'S' mintmark on a 1990-S proof penetrate the micro-thin 8-micron copper layer, exposing the silvery zinc core beneath.
Documented Benchmark Auction Records
Heritage Auctions Signature Sale. Highest certified grade for the issue, exhibiting blazing fiery copper mirrors and thick frosted cameo snow on Lincoln's portrait.
Stack's Bowers Rarities Sale. Certified within original U.S. Mint proof set packaging prior to holder encapsulation.
Common business strike without mintmark from a mintage of over 6.8 billion coins. Worth 1 cent in circulated condition.
Frequently Asked Questions
What is the 1990 'No S' Lincoln Cent error?
It is a rare proof Lincoln cent included by mistake in 1990 U.S. Proof Sets that lacks the San Francisco 'S' mintmark. Only an estimated 200–250 specimens were struck before the error was corrected.
I found a 1990 penny with no mintmark in change. Is it worth thousands?
No. The Philadelphia Mint struck 6,851,765,000 normal circulation pennies in 1990 without mintmarks. Unless your coin possesses deep mirror fields and came from a 1990 Proof Set, it is face value ($0.01).
How can you verify that a 1990 'No S' cent is a genuine proof?
Authentic proofs feature mirror-like fields, frosted high-relief portraits, squared wire rims, and no tool marks. Grinding off an 'S' mintmark removes the 8-micron copper plating, revealing the bright white zinc core.
What is the current value of a 1990 'No S' Proof Cent?
In PR-68 condition, values range between $3,000 and $4,000. Superb Gem PR-69 Deep Cameo examples have sold for over $7,000 at major auctions.
Can this error be found in 1990 Prestige Proof Sets?
Yes. A small number of 1990 'No S' Lincoln Cents were discovered in both standard purple-box 1990 U.S. Proof Sets and velvet-cased 1990 Prestige Proof Sets.
What is the FS variety number for this coin?
In the Cherrypickers' Guide to Rare Die Varieties, this error is cataloged as FS-01-1990-901 (FS-901).
Should I remove the coin from the original proof set packaging?
Do not remove it yourself! Submit the entire intact proof set to PCGS or NGC so their authenticators can document that the coin was housed in original mint plastic.