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CONECA (pronounced: CŌ´NECA) is a national numismatic organization devoted to the education of error and variety coin collectors. CONECA focuses on many error and variety specialties, including doubled dies, Repunched mintmarks, multiple errors, clips, double strikes, off-metals and off-centers—just to name a few. In addition to its website, CONECA publishes an educational journal, The Errorscope, which is printed and mailed to members bimonthly. CONECA offers a lending library, examination, listing and attribution services; it holds annual meetings at major conventions (referred to as Errorama) around the country.

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Doubled Die Basics

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  • #1

    Doubled Die Basics

    I have difficulty deciding whether those valued extra lines on a coin are mechanical or doubled die variety. I'm not sure what is meant by shelf-like appearance, especially when the mechanical has rounded ends and appear inside the center of the capital letter "O" and "D" (In God We trust). In addition, I use a 20X microscope for my research and it is difficult to see the "notching" effect the coin should display. I have viewed many, many coins which may or may not have been the doubled die variety.

    I have read many periodicals and articles on the internet, but I still cannot decide what is shelf-like and see the separation.

    Can someone drop a note to inform me what I should see when I'm trying to determine if the anomoly is "shelf-like" or not.

    Thanks in advance for your consideration.
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  • #2
    Shelf like doubling can be easily mistaken for a doubled die until you are able to identify it. This is one of my favorite coins for it pictures that affect clearly. This is a 1984-P Lincoln cent, which has a double ear, but is not a doubled ear.



    Look at this first picture and you can see that the TY of LIBERTY has some doubling. If this were a true doubled die, the doubling affect would be sen on mostly all the letters and just not these last two, especially considering the amount of doubling. This is flat, shelf like doubling, commonly refereed to as machine damage doubling or MDD. The next picture is from the same coin.



    Again notice that only certain areas have the doubling affect (indicated by white arrows) while the same design element has areas that are not doubled (black arrows). This is caused by the coin bouncing back up into the retreating die, flattening the areas that come in contact with the die for a second time after the initial strike. With this amount of doubling, one would expect to see some of that affect on the date, however, as seen in the next picture, the date is left untouched.



    Mostly, machine doubling damage is not consistent. In other words, it does not have doubling of a design element where it should have doubling. If this were a true doubled die, then the second picture, the facial features and LIBERTY would show consistent doubling through the whole design element and just not selected parts.

    I hope this helps and once you get the hang of telling the differences between other forms of doubling and a true doubled die, your searching will be a lot more fun

    BJ Neff
    Member of: ANA, CCC, CONECA, Fly-in-club, FUN, NLG & T.E.V.E.C.

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    • #3
      Dooubled Die Basics

      WOW!!! What a great reply...many thanks

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