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Errorscope
Our bimonthly journal, with current and back issues online for members.
Read the latest issueEst. 1983 · Knowledge Through Education
Devoted to the education of error and variety coin collectors
CONECA (pronounced CŌ´-NECA) is a nonprofit society of collectors who study, attribute and catalog the coins that left the Mint not quite as intended.
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Since 1983
Serving error collectors for over 40 years
39 representatives
36 U.S. and 3 Canadian
Errorscope
Our bimonthly journal
501(c)(3)
Tax-exempt educational charity
What we do
Everything an error collector needs
From your first doubled die to a lifetime of attribution, CONECA's members share what they know.
The Master List
The Error/Variety Index and Master List of attributed die varieties, by coin and date.
Browse the Master ListAttribution
Send a coin for attribution and listing, or bring it to a free examination at a coin show.
How attribution worksEducation
A lending library and educational programs, virtual and in person, for every level.
See upcoming programsArticles & Info
Explore the error-variety library
Decades of articles by CONECA's attributers and members, sorted by error type, coin series and feature.
Diagnostics of Fake and Genuine Unplated Zinc Cents
in Cents, Planchet errors
How to tell a genuinely unplated zinc cent from one that has been corroded, stripped by reverse electrolysis or re-plated — and the surface clues that give each away.
Brockage or Not? (Sandwich Coins)
Coins pressed together outside the Mint can pass for brockage errors. Here is how bent rims and telltale damage give these fakes away.
Rockwell Hardness Test Marks On Lincoln Cents
Why the Mint tests planchet hardness, what a genuine test mark looks like on a finished cent, and what is only damage.
Membership
Join CONECA
Membership is open to every collector, from first-time finders to lifelong specialists, in the U.S., Canada and beyond.
- Every issue of Errorscope, current and archived
- Free examination of your coins at shows
- Attribution and listing services
- Errorama, our annual meeting at major conventions
- The lending library and educational programs
- The members-only forum
Membership types
Regular
One collector, one year
Family
Everyone in one household
Young collector
Discounted, thanks to a generous donor
Already a member? Log in to renew
Articles & Info
Start learning
Plain-language guides to the errors and varieties collectors ask about most.
Doubled dies
When the die itself receives a doubled image during hubbing, every coin it strikes carries the doubling.
Read the guideRepunched mintmarks
Mintmarks once punched into dies by hand, sometimes more than once, leaving a second outline.
Read the guideClipped planchets
A blank punched from overlapping or misfed strip, leaving a curved or straight bite out of the edge.
Read the guide