Presidium Instruments Gem Tester II (PGT II) with Assisted Thermal Calibration (ATC) for Identifying Diamonds/Moissanites and Common Colored Gemstones Presidium Gem Tester Complete Unit is up for auction in Industrial & Scientific. The current bid is $26.55, 91% below the $289.00 MSRP, in As Is condition. This auction has ended — similar items appear in live auctions regularly.