The absence of any proof marks would indicate an American-made gun, but not much help in dating it aside from PetahW's fairly broad range.
It appears to be a fairly good quality gun, which would be consistent with Charles Daly's policy of buying high quality guns. It has, of course, Damascus barrels, so I would advise against firing it even if you can find 10 gauge shells. I think a date between 1875 and 1900 would be reasonable, but not certain, as many traditionalists wanted old style guns with hammers and Damascus barrels long after both were considered obsolescent.
Jim
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