It is a Sunset import of the early 1980's. It appears to be a model of the original O5's built by Baldwin in 1930 (#'s 5600-5607) as evidenced by the Elesco FWH. The oil tender is incorrect for this series of locomotives, but believe the oil bunker is removable. Also, it appears un-modernized, as it lacks a boxpok main driver. The oil-burning O5b's were built from 1937-1940 by the Q's West Burlington Shops and were characterized by Worthington FWH's. They were converted to oil burning from coal in 1950-1951 and were assigned to Lines West, based in Lincoln, NE (O5b #'s were 5614, 5620, 5626, 5627, 5629 and 5632).
It is one of Samhongsa's first efforts and holds up pretty well to today's standards.