Amsterdam banking crisis of 1763 in the context of Jan de Beijer

Abel Seyler (23 August 1730, Liestal – 25 April 1800, Rellingen) was a Swiss-born theatre director and former merchant banker, who was regarded as one of the great theatre principals of 18th century Europe. He played a pivotal role in the development of German theatre and opera, and was considered "the leading patron of German theatre" in his lifetime. He supported the development of new works and experimental productions, helping to establish Hamburg as a center of theatrical innovation and to establish a publicly funded theater system in Germany. Working with some of Germany's foremost actors and playwrights of his era, he is credited with pioneering a new more realist style of acting, introducing Shakespeare to a German language audience, and with promoting the concept of a national theatre in the tradition of Ludvig Holberg, the Sturm und Drang playwrights, and serious German opera, becoming the "primary agent for change in the German opera scene" in the late 18th century. Already in his lifetime, he was described as "one of German art's most meritorious men."

The son of a Basel Reformed priest, Seyler moved to London and then to Hamburg as a young adult, and established himself as a merchant banker in the 1750s. During the Seven Years' War and its immediate aftermath his bank Seyler & Tillemann engaged in an ever-increasing and complex, "malicious" speculation with financial instruments and went spectacularly bankrupt with enormous debts in the wake of the Amsterdam banking crisis of 1763, resulting in a decade of expansive litigation. Although they were wealthy bankers, Seyler and his business partner were "in no way representatives of the Hamburg bourgeoisie." A flamboyant bon vivant who was regarded with suspicion in Hamburg, Seyler symbolized a new and more aggressive form of capitalism.

Seyler & Tillemann was a Hamburg merchant bank in the 1750s and 1760s, that was owned by Abel Seyler and Johann Martin Tillemann. It involved itself in the currency market and "malicious" speculation with financial instruments during the Seven Years' War. It had ties to the brothers De Neufville in Amsterdam. Seyler & Tillemann went bankrupt as a result of the Amsterdam banking crisis of 1763 with 3–4 million Mark Banco in debts, an enormous sum. Its downfall also contributed to the downfall of other banking houses e.g. in Scandinavia.

In 1761 Seyler & Tillemann, acting as agents of their close business associate Heinrich Carl von Schimmelmann, leased the mint factory in Rethwisch from the impoverished Frederick Charles, Duke of Schleswig-Holstein-Sonderburg-Plön, a member of a cadet branch of the Danish royal family, to produce debased coins in the final years of the Seven Years' War. Seyler and Tillemann also owned a large silver refinery in Hamburg.