i have noticed here a common mistake:
the papal states arms are the opposite of what it is shown in the picture... the golden key is positioned to the left (not to the right).... the picture that you have now (for "Cancellarius Apostolicus") is that of the modern state of the "Vatican City".... when the arms were designed, the arms of the Holy See were chosen BUT in a mirrored way.....
but in the middle ages, they were either only golden or only silver.... we have accounts of both cases...
also, the background (yellow-white) is also modern.... the arms of the Papacy had red background....