Introducing Presidium’s Assisted Thermal Calibration (ATC) function using newly redesigned in-built calibration discs to ensure accurate and consistent tests for both indoors and outdoors operation. Presidium Duo Tester II (PDT II) is the only comprehensive tool on the market that combines two proven testing methods for gemstones. PDT II differentiates diamonds from its simulants based on both their thermal conductivity and reflective indexes. Coated gemstones can also be generally tested with the PDT II. The Presidium Duo Tester II comes with a probe pen that has a retractable probe tip which ensures consistent pressure against the gemstone during testing for more reliable results. With the industry’s thinnest probe tip size of 0.6mm, PDT II tests gemstones as small as 0.02ct. *Does not differentiate between natural and synthetic colored gemstones.