“Jewish Regulation” for Vienna [Habsburg Empire; Present-day Austria]: “[…] And when a Jew is here on business, he is to wear a Jewish sign in the front (of his clothing) – uncovered and undisguised – so that he can be recognized by Christians […] and so that a separation is maintained.”
Wertheimer, von Ritter, Joseph: Die Juden in Österreich: vom Standpunkte der Geschichte, des Rechts und des Staatsvertheils (1842) p. 61, Researched and Translated by Ziba Shadjaani 3/9/2016