Jewish Encyclopedia Volume 4 p312 states:

Soon afterward the magistrate, notwithstanding the duke's edict, permitted Jews as well as Jesuits to reside in Courland on the payment of 400 Albertus thaler annually; and the duke did not object to their admission (Gebhardi, "Gesch. von Kurland," p. 166, Halle, 17«9). In 1737 Duke Ernst Biron entrusted the court Jew Lipman (Levi) with the management of his finances, dividing the profits with him, and granting him certain privileges. This naturally created ill feeling against the Jews (Ersch and Gruber, "Encyc." section i. part 10, p. 247).