I'm an archaeologist, and I work in prehistoric times primarily. However, I've seen my fair share of stone. Over time you see enough things to make you develop a sense for things. And my instinct tells me that stone is not very old. Not at all. I very seriously doubt it's much older than 100 years, maybe mid-20th century. There is very little wear. The designs are cut very deep and 3-dimensional.

Looking at ecclesiastical coats of arms though, the tassels on the side are 15, denoting a cardinal. The wide-brimmed hat is a Catholic symbol which has been in use since the 1200's. The three fleur-de-lis surrounding the buck are a classical Catholic symbol, owing to several factors; usage by the royal houses of France (super Catholic families), having 3 tepals (Father, Son, Holy Spirit), lilies are mentioned many times in the Bible. Seeing fleur-de-lis on Christian regalia is exceedingly common, I don't think they have any unique meaning compared to other such heraldries. The stag too is a common Christian symbol, being mentioned in the Bible and being used frequently in these contexts. Crosses are crosses, you know what they are about. However, what we see is a Patriarchal Cross at the top. In a Catholic context these are most frequently associated with archbishops. An archbishop is lower in rank than a Cardinal. But, the Patriarchal Cross is also simply a cross variation.

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The little pope's hat is called a Mitre and is also very common on ecclesiastical coats of arms. It tends to denote people allowed to wear one, which I believe is anyone with a rank of bishop or higher (a cardinal would absolutely be allowed). The little curved thing to the right of the Patriarchal Cross is a Crosier, or a bishop's staff. The idea being it representing a herders staff. Keep in mind that most of these symbols and how an ecclesiastical coat of arms was supposed to look weren't standardized until the 20th century.

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What does the banner say at the bottom? I did some research and I believe this coat of arms may depict the coat of arms of William Henry O'Connell, Cardinal of Boston between 1907 and 1940. His coat of arms says 'Vigor in Arduis'. His coat of arms had shamrocks rather than fleur-de-lis though, so I might be wrong. Let me know if that sounds right.