PRESIDIUM Synthetic Diamond Screener II Bedienungsanleitung Seite 22

2.2 For mounted diamonds
Ensure that the stone is set with an open-back setting, meaning you
can still see a clear view and colour of the stone when you view the
back of it and it is not obscured by the jewelry metal or other stones.
(Fig 2.7).
Fig.2.7 An example of jewelry with open-back setting
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Clear and
unobstructed view
of stone through
the open-back