Your family had good taste Mike
It does appear to be in good shape, but of course should be checked by a qualified double gun smith before use.
It is a F grade made prior to WWI
Royal Steel is a fluid steel typical in composition to that used by all the U.S. double gun makers of that era.



A Research Letter would provide the exact DOM and possibly to where the gun was originally shipped
https://lcsca.clubexpress.com/content.aspx?page_id=22&club_id=43784&module_id=245742