There were three popes in the 20th C. who had served as Patriarch of Venice prior to their election to the papacy. (and two were also later canonized!) They each decided to retain a chief “of Venice” (with the winged lion of St. Mark, a symbol of Venice) in their papal coats of arms. The three were St. Pius X, St. John XXIII and Pope John Paul I.
The winged lion of St. Mark in chief is very striking. Great blog, Fr Sylvester.