Renowned as a silver coin of very high quality, this coin also has an important role in the history of Alchemy.  Johann Joachim Becher (1635-c.1682) is himself famous for having produced several examples of transmutation medals - medallions often inscribed with how they were converted from a base metal into alchemical gold - and he describes just that process in his 1665  Supplementum Secundum of his Physicam Subterraneam.  That process involves smelting Brabant Thalers - this very coin - with a flux of certain salts, a small amount of gold dissolved in aqua regia, quicksilver and other procedures.  This is then the very coin that Becher began his famous transmutations with and unsurprisingly, they were successful - Brabant thalers are now known to contain a small amount of gold, even giving them a slight yellow luster. A fascinating coin from the history of Alchemy and just a beautiful coin in general.
 
Brabant Thaler. Belgium, Duchy of Brabant, Albert & Isabelle (1598-1621), Patagon, without date (mid-to late 17th century), struck in Antwerp. Silver (0.875): 31 mm - 6.69 g. VF