Looks like it has rebounding hammers, so it would be 1880ish or later. Reilly was heavily involved in live pigeon contests in the 1880's and with the Jones underlever I'd guess it was built by SOMEBODY in the mid 80's.

Who built it is anybody's guess; I don't think we know for sure that E.M.Reilly ever built a gun at all. If he didn't, he sure must have been a great retailer though, because there are lots and lots of old Reillys still around...mostly of a distinctly higher than average quality...Geo