With the information given i believe you have a stag upper receiver group. The most important part of the upper is clearly marked stag and has the correct barrel specs stamped as well. Very few manufacturers will engrave the upper receiver on the mating surfaces between the upper and lower but most do not and i think stag would be included in the latter. I dont know if they perform the milling and finishing work on the upper receivers or if they source finished receivers from another company(ies). either way short of buying the gun directly from the manufacturer there isnt any way i know of to know for certain it was manufactured by stag or assembled by a third party with a stag barrel.