Wikipedia
In medieval and Renaissance Germany, the Münzwardein (also Wardein or Guardein, from the Latin word guardianus for guardian, protector) was the title of an official whose duties included supervising the Münzmeister and the stock of precious metals used in minting. He was responsible for the quality of alloys and the accuracy of weights and measures.
The Münzwardein was commissioned by the highest authority (generally a prince or a bishop). He was therefore the official representative of his principal in discharging his duty as an inspector of precious metals and precious metal goods in trade. It was his duty to produce weights used in minting and often he would also be charged with the safekeeping of minting irons when they were not used in producing specie.
The occupational name came from the French word gardien (= supervisor). Via the Northern French wardien and the Dutch wardijn the word entered the German language and replaced the previously used words Probierer (= tester), Hüter (= safekeeper) and Aufzieher (= puller). The first Wardein to be so called worked in mining. They were chemists working in mines and smelting facilities, where they were called on for their know-how in metallurgy. Frequently they doubled as goldsmiths and were required to separate auriferous silver from base metal.