Buckstix:

I think it unlikely that the original owner of your rifle was a lawyer. In the United Kingdom, esquire is a title of respect previously accorded to men of higher social rank, but which has since come to be used as a general courtesy title for any man in a formal context, usually appended to the name as in "John Smith, Esq.", with no precise significance.

Only in the U.S. has the term come to signify a license to practice law.

Rem