PRESIDIUM Synthetic Ruby Identifier User Handbook Manual page 24

2.2 For mounted jewelry or gemstones
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 2.6).
Fig.2.6 An example of jewelry with open-back setting
If your mounted open-back gemstone is in a ring, place the ring in the
centre of the cross-hair marking on the Ring Guide that is embossed
on the LED light source. The front of the mounted stone should be
directly facing the Photo-detector.
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