The Precious Metal Verifier PRO bring unparalleled diagnostic capability to the detection of counterfeit precious metal coins and bullion bars. This verifier greatly enhances the capabilities of the original PMV. It makes four separate measurements that ensures that the coin or bar contains valid metal. Measuring surface resistivity, and the resistivity ALL THE WAY THROUGH THE COIN OR BAR. No more worries about the depth of the buried metal. It measures the thickness of the metal, even for coins in plastic holders. You enter the listed or measured weight of the sample. It then makes sure that the length/width, or diameter of the sampe is consistant with its weight, resistivity, metal type, and thickness. It checks to ensure that the size of the object matches the metal that it's supposed to contain, which validates its density (specific gravity). With these additional checks, you will find greatly increased security using the Precious Metal Verifier Pro. Comes with durable carrying case. The External Bridge plugs into the multi-pin connector on the main body of the PMV PRO. It allows for thru measurements on bars between 12.5 and 45 mm thick that are at least 50 mm wide. This is the Pro base unit + an external bridge SET Also can update an existing PRO to an external bridge as upgraded add on. Must call in so the existing PRO can be calibrated to correspond with the new external bridge