Austrian 1520 Double Guldengroschen

The 1520 Double Guldengroschen from Austria was essentially a prototype for the thaler, influencing coin designs across Europe for centuries with its large, standardized silver content. Weighing around 60 grams and struck from high-purity silver, it aimed to unify currency in the Habsburg domains. Some specimens even bear the imperial eagle, a nod to Ferdinand I's ambitions.

Exact mintage figures are murky; records from that era often went up in smoke, literally, during later conflicts. What we know is it was produced in Hall, a key minting center, using planchets from local silver sources. Debates persist over whether it was meant for trade or as a prestige piece.

If you're hunting for one, good luck—most end up in museums, not collections. That's the nature of coins that started something big.