Jewish Encyclopedia Volume 2 p492 states:

Among the chief founders of the new venture was a Marano named Diego Teixera de Mattos; and of the forty original members of the bank twelve were Jews (Gratz, "Gesch. der Juden," x. 17, note). Later on, in connection with the Hamburg bank were the two Abensurs, financial representatives of the king of Poland. They represent another source from which Jewish capital was drawn; the position of the Jews as "factors" to the Polish nobility in some degree resembling the standing and functions of the Court Jews who slowly collected around the smaller German courts and who managed their finance much in the way modern banks do in the case of court estates.