The electors (Kurfürsten) were the seven German princes entitled to elect the German king; the archbishops of Mainz, Trier and Cologne, the king of Bohemia (in 1602 Rudolf II, the Holy Roman Emperor), the Count Palatine of the Rhine, the Duke of Saxony and the Margrave of Brandenburg. This theme was very popular around 1600 and was often represented in glassware.
Cf. G. Reineking-von Bock, Kataloge des Kunstgewerbemuseums Köln, Band IV, Steinzeug (Cologne 1976), p.245 ill.363
E. Klinge, Duits Steengoed, German Stoneware, Rijksmuseum Amsterdam (Zwolle 1996), p.76 ill.33 for other examples of Kurfürstenkrugen.