I would suggest that the lower receiver is a replacement, as well as the barrel nut. Serial number on the lower is different from what I am used to seeing on Inglis Brens, as well as the different finish from the upper. Barrel nut is Enfield produced. The butt also seems to have traces of the white band signifying DP. The butt also appears to have been replaced at one time, as evidenced by the Slaz manufacture. Interesting the C with the arrow through it. This is the same inspection mark we find on the Bren Plessey sights.....it's meaning or origin is a question.
The mag cover has the MA symbol on it, possibly representative of it's Australianservice. That style a chest is also indicative of some other country. Ours didn't have the bumper strip on the side.
All of these are normal mind you, considering that the rifle was FTR'd at one point, as evidenced by the marks on the left forward portion of the reciever.
Nice gun by the way. Good to see one that was not a re-assembled cut-up.