Can you tell a real Rockwell Test?

Discussion in 'Error Coins' started by Bobs Tavern Arm, Jun 19, 2019.

  1. A raised round angle press of a ball tip. This comes on the obverse of the 1956 Lincoln Cent struck with a cancelled die. (Yes I’m sending it in to PCGS) Why not. Error-Ref.Com says there have no recovered US Mint coins struck with a defaced die. There has been auction awareness of a cancelled die (Fred....)
    The last entry at the bottom on Part 3: Die Installation Errors. 185905A0-4BBB-42B9-861F-3B9A3751BAFA.jpeg
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  3. R_rabbit

    R_rabbit Well-Known Member


    I’m seriously interested in what pcgs says. Please update with photo s)
    Bobs Tavern Arm likes this.
  4. paddyman98

    paddyman98 Let me burst your bubble! Supporter

    I can't wait for your PCGS slab stating that you have an amazing find. Looking foward to it!
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  5. Pete Apple

    Pete Apple Active Member

    As I understand, you are saying this is a raised feature. That would indicate an indentation on the die which would certainly be from a Rockwell test on the die IF it had other characteristics of a Rockwell Test. I think it does not. The results of a Rockwell test on a die appear differently than a Rockwell Test on a planchet. This is because a Rockwell Test on a die uses a different Rockwell Indenter than on a planchet. It is a Rockwell B (more pressure) as compared to a Rockwell 15T on a planchet.

    The planchet test uses an indenter which leaves a hemispherical indentation. The ball indenter itself is the size of a 1/16" ball bearing and leaves an indentation about 1 mm in diameter. The indenter used for a B test on a die (because it is harder material) uses a sphero-conical indenter. The mark left will have sloping (not hemispherical) sides of approximately 120 degrees angle from the apex and will be circular at the edges greater than 1 mm in diameter. The mark on this coin does not show that.

    In addition, Rockwell testing protocol dictates at least 2 tests on a piece of material and you only mention one.

    This is not a Rockwell Test mark.
    Last edited: Jun 19, 2019
  6. paddyman98

    paddyman98 Let me burst your bubble! Supporter

    Excellent response. I agree.. But I doubt if the OP will accept it o_O..
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  7. Pete Apple

    Pete Apple Active Member

    Thank you!
  8. masterswimmer

    masterswimmer Well-Known Member

    Or care what was very eloquently written.
    The OP has an agenda this narrative doesn't fit ;)
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  9. Wanderingbark116

    Wanderingbark116 Active Member

    Your writing is amazing @Pete Apple !

    And @Bobs Tavern Arm please update as to what PCGS has to say! If we don't hear from you about it, I'll have to assume you took your ball and went home because you didn't want to play anyways.
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  10. Pete Apple

    Pete Apple Active Member

    Thank you @masterswimmer. I am thinking that the value in my taking the time to respond in such a way is not necessarily for the OP, but as an educational and informative contribution for others who may be interested or otherwise stumble across this thread.
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  11. Pete Apple

    Pete Apple Active Member

    Thank you!
  12. Michael K

    Michael K Well-Known Member

    I believe Fred has answered this in other threads that there would be no way to tell.
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  13. Pete Apple

    Pete Apple Active Member

    I think Fred is correct, however there are circumstances in which a mark can be identified as "likely".

    Elsewhere, I have noted the following with regard to a test mark on a planchet:

    "We are accustomed to thinking that if an imperfection on a coin satisfies the diagnostics associated with a particular mint error, then we can assign it to that mint error. For example, a cud (marginal die break) is unlikely to be confused with any other defect. In other words if it looks like a duck, walks like a duck, and quacks like a duck, then it is a duck!

    However, with a Rockwell Test Mark, this way of thinking may not be appropriate. It may be possible for an indentation to match the description of a Rockwell Test Mark without actually being a Rockwell Test Mark. The only way I know to be certain that a mark came from a Rockwell Test is to have actually witnessed the test which, of course, is not possible! The most we can say is that a particular indentation meets the expectations of a Rockwell Test Mark. A Rockwell Test Mark should have a smooth, hemispherical cross section profile and assume the shape of a circle or an oval (if it is adjacent to a device). There should be no anvil effect (a raised area on the opposite side of the coin) and no pressure ridge around the circumference of the depression.

    I know the odds are low that a Rockwell Test Mark will make it through the minting process. I am also thinking that the odds are low – or even much lower – that a random contact mark on a coin

    • would have the same hemispherical cross-sectional profile as a Rockwell Test Mark AND
    • show the same depth as a Rockwell 15T test mark AND
    • have the same diameter as a Rockwell 15T test mark (adjusted for the strike) AND
    • not leave a pressure ridge AND
    • not leave an anvil effect (bulge) on the opposite side of the coin.

    I know of no way to calculate the probability of all those things occurring as a result of random post-mint damage – but I think it would be astronomical. It would be even more improbable for all these things to occur twice on the same coin as the result of random post-mint contact..."

    Since a mark can only be identified as "likely" I think that a TPG will never certify a mark as being a Rockwell test Mark. I, too, will be interested in hearing the response of PCGS!
  14. Fred Weinberg

    Fred Weinberg Well-Known Member

    Pete Apple - IF you send it to PCGS (or NGC for that matter)
    Please make a note on the submission flip itself that you believe
    there is a RTM in this 'xxx' area. That will help me focus on the
    area of the coin.

    However, I can tell you that based on your photo, and seeing the Rockwell
    Test being done at the West Point Mint (about 12 years ago), you should
    save your submission/postage fees. It was being used on Silver Eagle planchets.

    It is my understanding, and I am checking with another source for verification)
    that the Rockwell Test is not performed on U.S. Dies.
  15. Pete Apple

    Pete Apple Active Member

    Fred Weinberg - thanks!

    Just to clarify...this is not my coin in the photo by the OP.

    Also very interested to learn the answer to Rockwell Testing on dies...whether or not done by the Mint. Even if not done by the mint I am thinking a die slipping through with a test mark done by the supplier might still be a remote possibility (or does the Mint cut the rods in order to make the dies?)

    I do know that the US Mint purchases the die steel in spheroidized annealed condition with certified capability hardness to a min Rockwell-C.
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  16. Fred Weinberg

    Fred Weinberg Well-Known Member

    Pete - I see my mistake - hope the OP reads
    my reply.
  17. Pete Apple

    Pete Apple Active Member

    FYI - I have received a communication from the Mint that Rockwell Hardness Testing (C Scale) is performed by them on production dies.
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  18. Fred Weinberg

    Fred Weinberg Well-Known Member

    Can you share that communication with us please?
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  19. Pete Apple

    Pete Apple Active Member

    Here is copy and paste. I could also forward or send as .pdf to an email address. Here I have blanked out my email.

    Inquiries <>
    Wed 6/19/2019 2:27 PM

    Dear Mr. Apple,

    Thank you for your question concerning the quality of United States Mint dies.

    Yes, the United States Mint performs hardness testing on production dies. We use the Rockwell-C hardness scale.

    We appreciate your interest and hope this information is helpful.


    United States Mint

    From: Pete Apple <>
    Sent: Wednesday, June 19, 2019 10:29 AM
    To: Inquiries <>
    Subject: Quality of dies question

    Can you tell me if the US Mint does Rockwell Hardness Testing on selected dies before they begin production. If so can you tell me which Rockwell Scales are used? I know that Alloy 52100 for small diameter coins and L6 for quarter on up is used.

    Thanks for your help,

    Pete Apple
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  20. Fred Weinberg

    Fred Weinberg Well-Known Member

    Interesting - is the Rockwell -C hardness scale for dies done the
    same way as the Rockwell Test for planchets?

    I'm not a techie, so I don't know what Rockwell-C means exactly.
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  21. Pete Apple

    Pete Apple Active Member

    Rockwell C Scale: Preliminary Force = 98.07N (10 kgf) Total Force = 1471N (150kgf)
    Rockwell B Scale: Preliminary Force = 98.07N (10 kgf) Total Force = 980.7N (100kgf)
    Rockwell 15T Scale Preliminary Force = 29.42N (3 kgf) Total Force = 147.1N (15kgf)

    Another type of Rockwell Test Mark which may be found on Lincoln cents is a raised bump. If there is an indentation on a die caused by a Rockwell Test, then it would be transferred to the coin as a bump during the strike. I think it is important to understand what appearance we might expect this bump to take.

    Steel for dies is supplied to the U S Mint by Latrobe Specialty Steel Company, a Division of Carpenter Technology. The steel alloys are Alloy 52100 for small diameter coins and Alloy L6 for quarter on up. They are sold in the spheroidized annealed condition to a maximum Rockwell C hardness and certified capability hardness to a minimum Rockwell C hardness level. Everything is in Rockwell C scale. This hardness range is approximately 33 to 58 Rockwell C hardness.

    Alloy 52100 is a deep hardening steel alloy used for aircraft bearings and other high stressed parts where good rolling contact fatigue strength is required at temperatures below 400⁰F. Its typical composition is 1.05% C, 0.35% Mn, 0.30% Sn, 1.50% Cr, and the balance Fe. (Latrobe, 52100)

    Alloy L6 is a versatile oil-hardening tool steel that is characterized by good toughness and is suitable for tools, dies and machine parts. Its relatively high nickel content gives it greater impact toughness. Its typical composition is 0.70 C, 0.60 Mn, 0.25 Si, 0.70 Cr, 1.40 Ni, and the balance Fe. (Latrobe, L6)

    The level of hardness of these steel alloys requires testing with the Rockwell C Scale. The requirements for using this scale with this level of hardness necessitate the use of a spheroconical diamond tipped indenter. This means that the resulting indentation will have a different conformation than the hemispherical shape.
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