Dear RickyP;
Our esteemed associate, Elle is 100% correct in her announcement that the crossed keys symbolize the Papal See. The crossed keys, most often represented as a gold key and a silver key, represent the twin kingdoms of Heaven and Earth. Jesus spoke to St. Peter and stated:
et tibi dabo claves regni caelorum et quodcumque ligaveris super terram erit ligatum in caelis et quodcumque solveris super terram erit solutum in caelisMatt.16-19
Translated:
And I will give to thee the keys of the kingdom of Heaven. And whatsoever thou shalt bind upon earth, it shall be bound also in heaven: and whatsoever thou shalt loose on earth, it shall be loosed also in heaven. Matt. 16-19
In stating this to St. Peter, Jesus established the twin kingdoms of Heaven and Earth and thus the golden key represents the eternal kingdom of Heaven and the silver, the temporal kingdom of Earth.
Also, please note that the crossed keys are part and parcel of the ancient Roman Catholic symbolisim associated with ecclesiastical heraldry and as such, are reserved strictly for use of the presiding Pope, therefore a Cardinal or Bishop can not use the crossed keys as part of their heraldic coat of arms or as a part of a representation.
Please note that our Lady, the Virgin Mary, always has Her venerated name abbreviated merely as M. therefore the statement issued by Elle that M.A. might represent Maria Assumpta is highly likely.
Taking these rules into consideration, we can now determine that the person depicted on the medal is a Pope. And so, the only question is WHICH Pope? To assist in resolving the mystery, I should like to remind everyone that the facial depiction on the medallion is somewhat clear, so this should assist us in our answer.
Also, as a hint, I would like to remind everyone that the Vatican City is a Papal
STATE. And all states issue one item, which should be of help in identifying the mystery Pope.

Your friend;
LAMAR