The visitation lists, which noted among other details the occupations of the Frankfurt Jews, show moneychanging and moneylending as the most frequent occupation.
There were many different kinds of money in circulation in Germany as a result of its division into many small states, and one of the functions of moneychangers was to establish the relative value of these currencies and exchange them for a fee.
The situation was particularly confused in the 16th and 17th centuries.
The money market was flooded with coins whose precious metal content was lower than their face value, leading to uncertainty in trade and price increases.
As a centre of international trade, Frankfurt was particularly hard hit by these problems.
Jews, who had early moved into moneylending as a major activity, were regarded as the best judges of the confused currency market.
They were also involved in dealing in commercial bills, which had come into general use since the 16th century and were a form of credit and also a means of cashless payment.
Historically, the free market in these bills developed out of moneychanging, and for a long time the two activities were so closely linked that it is not always possible to determine which was more important.
Despite the frequent mention of Jewish moneychangers, it is important to remember that there were also many Christians engaged in this activity.