A Jewish doctor goes to a tailor with all of the foreskins that he gathered from circumcisions. He tells the tailor that he wants something useful made out of them. A few days later he goes back and the tailor hands him a wallet made out fo the foreskins.

The doctor says "That was a lot of foreskin and all i got is this small wallet?"

To which the tailor replies, "When your rub it it turns into a briefcase."