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13936Re: Rockwell test mark

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  • Mike Diamond
    Jun 24, 2006
      This appears to be post-strike damage, but of a special sort. It
      looks like a mild manifestation of "ejection impact doubling". This
      occurs when a finished coin is thrust back into the die face by the
      ejection mechanism. This leaves pits and dents (and sometimes
      recognizable design) on the surface of the coin. Recognizable design
      elements are widely scattered and often widely separated from their
      normal counterparts.

      The lip is a frequent location for this to occur.

      --- In errorcoininformationexchange@yahoogroups.com, "Jeff"
      <jylitalo@...> wrote:
      > (uploaded to default folder)
      > First 4 pictures are of four differnt Sac dollars showing this mark.
      > The fifth picture is a close up of coin #3 taken sidelong, down into
      > the indent with the best light I could manufacture.
      > I dont see a pressure ridge, they are all very smooth both at the
      > of the indent and inside the indent.
      > Also, the Sac Dollars I have with this paticular indent do not
      > share the same die pair. This indent is not confined to just one
      > striking die. As far as I've been able to tell, this only shows up
      > these dollars that have a form of doubling present. (At least this
      > my accumulated observation).
      > This has had me on again, off again, trying to figure out what is
      > going on.
      > The Rockwell test Mark is only to determine hardness?
      > Would the test be conducted more often in the first year that a coin
      > design is struck? Certainly there were a good variety of happenings
      > in 2000 with the Sac dollar, the rinse, the experimentals....
      > Perhaps more to the story?
      > > I am going to post a set of four Pic's in the default albumn and
      > > what you think.
      > >
      > > Sometimes the mark (indented pock) is tiny, but there. Sometimes
      > > is easily visible and a bit bigger. I cannot detect a pressure
      > > and the indentations are all very smooth. They are not a perfect
      > > circle.
      > >
      > > If the 71 S cent wasn't in the default folder to begin with so I
      > > see it, I'd have never got myself started back on this cold trail
      > > curiosity:)
      > >
      > >
      > > --- In errorcoininformationexchange@yahoogroups.com, "Mike
      > > <mdia1@> wrote:
      > > >
      > > > I've posted a picture in the Default album of a Rockwell test
      mark on
      > > > the reverse of a 1971-S cent. Notice the very smooth surface
      of the
      > > > indentation and the complete absence of a pressure ridge.
      > > >
      > > > Test marks can be on the die or the planchet. Both need to be
      > > > checked for proper hardness.
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