Arguably one of the best coats of arms designed and emblazoned by the late Archbishop Bruno Heim was that of Pope John Paul I who reigned as pope for just 33 days from August to September of 1978. The coat of arms was slightly modified from the one he had borne before becoming pope. Upon his election Albino Cardinal Luciani chose the unique double name of John Paul combining the papal names of his two immediate predecessors. The coat of arms was put together to reflect this double name. In chief we see the lion of St. Mark that makes up the arms of the See of Venice. Cardinal Luciani served as Patriarch of Venice before being elected to the papacy. In addition, two of his predecessors as pope, St. Pius X and Bl. John XXIII also were Patriarchs of Venice before their respective elections as pope and both retained the chief of St. Mark in their coats of arms as pope. In the arms of John Paul I the chief of St. Mark not only recalls his own time in Venice but evokes the memory of Pope John XXIII. The collee, or stylized mountains or hillocks in base are from the coat of arms of Pope Paul VI whose family name, Montini, means “little mountains”. In between the mountains and the chief there are three stars. Paul VI had three fleur-de-lis in the same position in his arms and Cardinal Luciani’s original arms had three stars but the stars had only four points each. Here they have been modified to five-pointed stars which are a heraldic symbol of Our Lady, specifically of the Assumption. Despite the fact that Pope John Paul I adamantly refused to be crowned as pope the papal tiara nevertheless appears in its usual spot ensigning the shield along with the keys of St. Peter. Truly, this is one of Heim’s best designs. Sadly, it was not seen by many because of the brevity of the pontificate of the “smiling pope”.
EXARANDORUM 
I prefer the arms of Paul VI, also designed by Bruno Heim. This has the chief of Venice with metal over metal, like the arms of John XXIII.
I agree that Paul VI also had a nice coat of arms but it was NOT designed by Heim. The arms used by Paul VI were the arms of his family and he used them as a bishop long before he was elected pope. He made no change to his arms after he was elected pope.
The chief of Venice is of ancient origin and while it does place a metal on a metal (gold on silver) that is not as bad as many people think it is. There is an impression in heraldry that there is a definite “rule” against this: the so-called “tincture rule” that must always be observed. Rather, this “rule” is merely a custom that should be observed because it embodies a principle of good design. Namely, to make things easier to discern. However, there are many, many examples of metal on metal in heraldry…including in the coat of arms of Bruno Heim himself which shows a gold lion on a silver field! In fact, Heim wrote an entire book about it called “Or and Argent” in which he illustrates copiously with many examples from ancient history to the present day where there are “violations” of the tincture “rule”. I think the arms of the See of Venice are a good example of where this rule can be overlooked and do not represent an example of bad heraldic design.