Featured Learn About Die Doubling...

Discussion in 'Error Coins' started by jtwax, Jan 21, 2005.

  1. jtwax

    jtwax Senior Member

    How Doubled Dies are Created and Their Classes.

    Determining Die Doubling from Other Forms of Doubling. (Requires Acrobat Reader)

    Take the Doubling I.Q. Test.

    Doubling: Worthless or Valuable?

    What is an RPM or OMM?

    Two exciting varieties to collect. Two formidable tasks that require a steady stream of knowledge, information and most importantly, help. If you decide to explore their potential enjoyment and challenge then here is some information and perhaps a little, help.

    You should be familiar with the minting process before you dwell to deeply into acquiring RPMs and OMMs. It would be wiser to have more than just a cursory knowledge of the minting process of course, so it is recommend that you try to obtain a book or reference on this subject when you can.

    RPM and OMM varieties are closely associated with the DIE as part of the overall minting process, so it is also highly recommended that you at least perceive how a die is created and obtain reference materials on this specific subject too. As you read this RPM and OMM information, you will understand the importance of gaining knowledge about the die-making process.

    At the Mint, a die is created. When the die is almost finished by the mint workers there comes the task of placing the Mint mark on the die before it will be used to produce millions of coins (pre-1990).

    The Mint employee who puts the Mint mark on the die is commonly referred to as the ENGRAVER. The engraver is sitting behind a counter or table. In front of him or her will be clamps or a device commonly know as a "vice". The die is secured between this clamp or vice so it will not move during the remainder of this process. On the table nearby, the engraver will have a detailed sketch or drawing of the coin design. On this drawing there will be a special highlighted area where the Mint mark is to be placed. By "area" we are referring to a specific designated place on the die that is much wider and longer than the actual size of a Mint mark. There is plenty of room or latitude for the engraver to work within. This latitude explains why you will find a "S" Mint mark say, for 1955 cents, in different locations under the date. For instance, on one die for 1955 S cents the Mint mark was placed just to the right or east under the "9" of the date. On another die the Mint mark is found directly under the "5" of the date. Both Mint marks are within the space or area shown on the sketch, yet in different locations therefore within the Mint "standards".

    The Mint mark punch is typical of punches you can purchase at any hardware store. At the Mint, the shaft of the punches are color-coded by using different colors of paint so the engraver can easily determine which punch has the Mint mark of "D" or "S" and so on. The shaft of the punch is "V" shaped. This "V" shape grooving on the side of the shaft allows the engraver to readily "feel" that the punch is in the proper upright (or normal) position. At the end of the punch is the letter of the Mint mark in its normal size, shape, etc.

    The engraver looks at the sketch and the location or area where the Mint mark is to be positioned or placed. Once the engraver is satisfied that the "V" shaped grooves are in his hand correctly and that the tip of the punch that has the Mint mark of "D" or "S", etc., is the proper position, the thick end or top of the punch is hit firmly by a mallet.

    How hard is the punch hit? However hard the engravers experience, expertise, judgment and ability deems appropriate. How many times is the punch hit? However many times the engravers experience, expertise, judgment and ability deems appropriate. No one really knows the answer to this question. But one thing is for sure - Variety collectors can at least intelligently guess how hard and how many times. That's one of the primary reasons they collect these varieties in the first place!

    It is generally accepted consensus of RPM and OMM collectors that the engraver strikes the punch with the mallet more than one time in order to assure that the Mint mark is sufficiently imprinted into the die face. However, it is equally noteworthy that many times the Mint mark is placed on the die with only one blow to the mallet in the opinion of some experts.

    RPMs occur after the engraver strikes the mallet with the first blow to the top of the punch. Remember that the Mint mark punch is hand held and struck by the mallet in this manner. After the first blow, the engraver will check that the Mint mark has been placed inside the designated area that is on the sketch. A careful check will also be made to assure that the Mint mark punched into the die is clearly visible and sufficient enough for the coining process. If, in the judgment of the engraver, another blow with the mallet is required the punch is placed back on top to the original Mint mark and struck again, or again, or again, or .... until the engraver is satisfied. It is also possible that the initial blow from the mallet to strike the Mint mark could cause a "bounce" of the punch, thus creating a doubled, tripled, or more Mint mark punch.

    The exact repositioning of the tip of the punch on top of the Mint mark already placed on the die requires a steady hand, keen eyesight, and solid nerves. If the Mint mark at the tip of the punch for the second strike is not positioned exactly on top of the existing Mint mark then a RPM has been created. If a third, fourth, fifth, six, etc., blows occur then multiples of the Mint mark can and have appeared. This inaccuracy is the foundation for the joy of searching for RPMs!

    An OMM is a coin that has two (2) different letters or Mint marks punched into the same die. It is generally accepted by the RPM and OMM variety community that there are two primary reasons why a die would have two distinctly different Mint marks.

    The first reason is premised upon economic measures instituted by the Mint. A die already has, say, a "D" Mint mark in the die. The die is in such a condition where it can continue to be used to produce coins, so a decision is made by the Mint to use the "D" Mint mark die for "S" Mint mark coins. It is ordered that a "S" be punched on top of the original "D". The "S" Mint mark coins with the "D" underneath are produced and a OMM is created for the collector!

    The second reason is not associated with Mint policy, practices, or cost-saving efforts, but rather, a unintentional mistake by the engraver. Remember that the punch the engraver used is colored so they would know which punch had a "D", "S" etc. Picture that the engraver has a die which requires a "D" Mint mark. The "S' punch is unintentional picked-up and the blow by the mallet is struck. The engraver is checking this first blow to be assure it is inside the area shown on the sketch. The engraver sees the "S" Mint mark was used and not the "D". An error has occurred. Instead of discarding the die the engraver simply takes the correct "D" Mint mark punch and "covers" his mistake with it via several blows to the mallet. No harm done. The die is usable for its life in the coining press.

    Conversely, the engraver may not even notice that a "S" has been placed on the die intended for a "D". An interruption, break, lunch, etc., and the engraver returns to the task at hand. Pick-up the colored punch with the "D" Mint mark and strike one or more blows to the mallet without looking at the original or error "S" Mint mark that is showing. The engraver unintentionally made a mistake and never knew it. If the engraver did look and did see the "S" no one but the engraver will ever know.

    RPMs and OMMs come in many different forms and configurations. No in-depth discussion of these attributes is necessary right now, but for your enjoyment of "the hunt", RPMs and OMMs can be found in a vertical over horizontal position: a vertical over inverted position: on top or under the number (s) of the date: with two totally separated Mint marks: even tilted: and, the overlapping of a Mint mark once or several times in succession.

    If terms such as "inverted" or "vertical" or "tilted" seem confusing, even contradictory, when thinking of the engraver sitting there at the bench with the punch in hand that is waiting to be struck by the mallet then welcome to the great realm of RPM and OMM collecting! Whatever you do, don't fret over the terms.

    Lastly, don't forget that since 1990 the Mint mark has been made directly on the die. There will be no true RPMs and OMMs from 1990 to the present. No big deal, though. There are thousands and thousand out there in variety-land just waiting to be collected and discovered... by you!

    - by George Wilkinson
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  3. susanlynn9

    susanlynn9 New Member

    Fascinating reading! Thanks so much for posting this :)
  4. cdb1950

    cdb1950 Senior Member

    Cool! Thanks!
    Zorrbabe likes this.
  5. cdb1950

    cdb1950 Senior Member

    Would it be possible to make this a 'STICKY' so that it would always remain at the top of this column? It is a great reference and should readily be available instead of getting lost as new messages are posted.
  6. susanlynn9

    susanlynn9 New Member

    I agree. This is a very informative post and I think it would help people tremendously if it were a sticky at the top.
  7. KAHedge

    KAHedge New Member

    Good reading! I spent several hours going through 73 each 1971 Blue Ikes and came up with a WRPM-004 RPM that is graded at MS-64. Patience and tenacity were certainly virtues.
    Zorrbabe likes this.
  8. Murphy

    Murphy New Member

    Just what I needed.
    Zorrbabe likes this.
  9. mikediamond

    mikediamond Coin Collector

    All excellent references. Pleased be advised, though, that "abrasion doubling" is largely a myth. The vast majority of coins paraded as examples of "inside die abrasion doubling", "outside die abrasion doubling", or "die polish doubling" are simply cases of die deterioration doubling.
    Zorrbabe, Insider and Rachael like this.
  10. jtwax

    jtwax Senior Member

    Thanks Mike! :)
    Zorrbabe likes this.
  11. Morgan

    Morgan New Member

    Need help with a possible Double Die Kennedy

    I was looking through some Kennedy Halves and I came across this Bicentenial coin. I think that it is a Double Die Error. The area in question is the date specifically the right side or the 1976. It appears to me that the 9, 7, and 6 show possible doubling.

    I have tried my best to provide clear and legiable picture which emphasize the doubling, however the pictures are nothing compared to how this looks in a 20X loupe.

    From what is shown in the following pictures does the date show doubling? Or should I invest in better glasses?:cool:

    Attached Files:

    David Eugene Swiger likes this.
  12. mikediamond

    mikediamond Coin Collector

    This appears to be die deterioration doubling. The late die state would be consistent with this diagnosis.
    Zorrbabe and Kelly Capone like this.
  13. Morgan

    Morgan New Member

    I have found two other coins in my recent search which show doubling as well I believe they exhibit the same type of doubling. I am hoping for a second unbiased opinion so I won't mention the form I believe these two exhibit. I want to make sure I understand doubling and how to recognize the forms.

    Both have occured in the script which follows around the outside of the reverse of a 1974-D Kennedy Half Dollar. The first two picture are from the first coin and the last three are from a second coin.
    I would really like to hear your opinions and appreciate any responses.:D

    Attached Files:

    Kelly Capone likes this.
  14. mikediamond

    mikediamond Coin Collector

    This appears to be machine doubling, a.k.a. "mechanical doubling", "machine damage doubling", "machine doubling damage", "strike doubling", "ejection doubling". The flat shelving along the edge of each letter is characteristic.
    Kelly Capone and coinzip like this.
  15. NICK66

    NICK66 Coin Hoarder

    Mike, my problem with that doubling is that I've seen coins that had the exact same type of doubling and its been slabbed "double die." I don't get it. I will try and find a couple so you can see what I'm talking about.
    Zorrbabe and GONZA713 like this.
  16. mikediamond

    mikediamond Coin Collector

    The coins you saw may have been encapsulated by low-budget slabbers. If they used the term "double die", that's a dead giveaway they don't know what they're doing. The correct term is "doubled die". A true doubled die will not show flat shelving. Instead you'll see furrowed letters and numbers, split serifs, and often subequal strength of both images.
    Alessio Sena and GONZA713 like this.
  17. Morgan

    Morgan New Member

    The coins were actually in circulation and were found by me. Part of a $100.00 on halves I was searching. I was pretty sure they were strike doubling errors but as I am new I wanted to get a confirmation.

    After finding these two I found two more. One on a 78-D and one on a 71-D. Im begining to think that strike doubling is preety common.
  18. Dani05

    Dani05 Member

    German Doublings

    i'm new here and from germany, where double dies are also popular...

    this is a very good thread to inform people about doublings... :)

    if you are interested in seeing some german doublings, here is an very impressiv example:
    (if advertising is not allowed, i can delete it)

    edited - you are correct, advertising is not allowed

    best regards,
  19. foundinrolls

    foundinrolls Roll Searching Enthusiast

    Mike is absolutely 110% correct. The doubling is the flat shelf-like mechanical doubling that I've seen on well over half a million coins. Coins struck by doubled dies look vastly different.
    Check out the notches as seen on the word WE on this example of Die doubling on a 1966 Half. It is totally different than the flat doubling.
    Have Fun,

    Attached Files:

    • we2.jpg
      File size:
      12.4 KB
    NewCollectorRick likes this.
  20. Just Carl

    Just Carl Numismatist

    True this is a great thread and educational. Unfortunately at coin shows around here even the dealers are so unaware of these many types of errors that there is very little value to them. Unless an error coin has made it into the big time fame, such as 1955DD Lincoln Cent, there is little value except if your an error coin collector. Usually only very visable errors are of any value. I've slowly collected hundreds of varieties of error coins and few could be sold for more than a regular coin. Still this is the kind of information I print out.
    Kelly Capone and Nick Chiappetta like this.
  21. Dani05

    Dani05 Member

    what kind of doubling

    hello, what kind of doubling are the following coins?






    thank you for your help!!! :bow:
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