Reference metal for precise calibration.
 This is a sample of a high-purity metal (+ 99.9%) which is used to detect fluctuations in measurements due to temperature differences,  To compensate for changes in the electrolyte or other influences.
 Your  Measuring device  tested for full functionality, measurement deviations determined and measurement errors avoided.
 It is particularly important to adapt the device to this metal when searching for a specific metal. The reference metals are used for this.
 When searching for gold, the device should also be matched with a reference made of pure gold for the most accurate results possible.