Digital refractometer by Presidium (model Prim II) Digital scales - regular lines - resolution 0.001g Hold the light button to

Hold the light button to adjust brightness

If you remove the cap for the first time after two or three years

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Digital refractometer by Presidium (model Prim II) Digital scales - regular lines - resolution 0.001g Hold the light button toSummary Made by Presidium, the leading manufacturers of gem testing equipment. There is downloadable software to connect it to your computer. The reading is then displayed along with a list of stones that match the reading, and you can click on each stone to see more information (constants). This saves time looking up charts. Comes with a USB cable (connects to any computer mobile device USB mains adaptor). Works with loose stones and also stones