I think Tom was refering to the state of Maine in the U.S.A. The outline of the mark does bear a resemblance to the State's boundaries.
Checked my American and Canadian references, but could not find that exact mark. One possibility might be Towle Silversmiths, Newburyport, Massachusetts. They had a Paul Revere trademark that had the letters P and R in script. The problem is, I have only seen the PR letters in a rectangle shape cartouche.
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Best regards,
Pat.
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