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Kennedy-half error, weird surface sheen. Help!

Please help identify this error. There is an unusual sheen on the obverse and revers surface. The shiny area extends out from the center of the devices into the field. It is on both sides of the coin, but is represented better in the oberse image below. Also both devices are distorted in the area of this shiny surface but the edges of the coin outside the sheen and distorted devices seem sharply struck.

I think I may have read a description of this problem in the "Readers Ask" section of CoinWorld a few months ago, but as I recall I don't think the explanation was very explicit.

Does anyone have an opinion on what caused the shiny area and the distorted devices on this coin?

Thanks.

imageimage
"Please help us keep these boards professional and informative…. And fun." - DW
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BONGO HURTLES ALONG THE RAIN SODDEN HIGHWAY OF LIFE ON UNDERINFLATED BALD RETREAD TIRES

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    cheezhedcheezhed Posts: 6,338 ✭✭✭✭✭
    Struck through grease?
    Many happy BST transactions
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    fcloudfcloud Posts: 12,133 ✭✭✭✭


    << <i>Struck through grease? >>



    yup!

    President, Racine Numismatic Society 2013-2014; Variety Resource Dimes; See 6/8/12 CDN for my article on Winged Liberty Dimes; Ebay

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    DieClashDieClash Posts: 3,688 ✭✭✭


    << <i>

    << <i>Struck through grease? >>



    yup! >>



    Thanks for that. So how does the grease make the surface so shiny? I can understand how alot of grease, evidently filling both dies could cause the flat and distored devices upon striking the planchet. But why does it also make the surfaces so shiny?

    "Please help us keep these boards professional and informative…. And fun." - DW
    ---------------------------------------------------------------------------------------------------------------------------------------
    BONGO HURTLES ALONG THE RAIN SODDEN HIGHWAY OF LIFE ON UNDERINFLATED BALD RETREAD TIRES
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    fcloudfcloud Posts: 12,133 ✭✭✭✭
    The grease has filled to pours of the die too. Makes it shiny

    President, Racine Numismatic Society 2013-2014; Variety Resource Dimes; See 6/8/12 CDN for my article on Winged Liberty Dimes; Ebay

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    DieClashDieClash Posts: 3,688 ✭✭✭


    << <i>The grease has filled to pours of the die too. Makes it shiny >>



    Thanks fcloud. I didn't realize the dies were so porous, but that makes sense. It's almost a prooflike surface quality without the mirrored appearance.
    "Please help us keep these boards professional and informative…. And fun." - DW
    ---------------------------------------------------------------------------------------------------------------------------------------
    BONGO HURTLES ALONG THE RAIN SODDEN HIGHWAY OF LIFE ON UNDERINFLATED BALD RETREAD TIRES
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    FredWeinbergFredWeinberg Posts: 6,029 ✭✭✭✭✭
    The dies are not pourous at all.

    The "grease" or foreign matter
    is coming between the planchet
    and the hard dies, at about
    45 tons of pressure (could be
    diff. now with the newer presses).


    It's the "grease" that makes
    either the rough surfaces, or the "shiny-er"
    surfaces on the struck coin.

    It will depend on what foreign material
    is on the dies or the planchet.
    Retired Collector & Dealer in Major Mint Error Coins & Currency since the 1960's.Co-Author of Whitman's "100 Greatest U.S. Mint Error Coins", and the Error Coin Encyclopedia, Vols., III & IV. Retired Authenticator for Major Mint Errors for PCGS. A 50+ Year PNG Member.A full-time numismatist since 1972, retired in 2022.
  • Options
    DieClashDieClash Posts: 3,688 ✭✭✭


    << <i>The dies are not pourous at all.

    The "grease" or foreign matter
    is coming between the planchet
    and the hard dies, at about
    45 tons of pressure (could be
    diff. now with the newer presses).


    It's the "grease" that makes
    either the rough surfaces, or the "shiny-er"
    surfaces on the struck coin.

    It will depend on what foreign material
    is on the dies or the planchet. >>



    Thanks Fred!

    This is why I post on these boards. The quality and breadth of knowledge contained in the responses is immeasurably valuable.

    image
    "Please help us keep these boards professional and informative…. And fun." - DW
    ---------------------------------------------------------------------------------------------------------------------------------------
    BONGO HURTLES ALONG THE RAIN SODDEN HIGHWAY OF LIFE ON UNDERINFLATED BALD RETREAD TIRES

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