Thank you so much for offering a mag catch... but I couldn't impose.
I also encountered two problems(?) while cleaning and oiling for the first time.
First, one of the pins that holds the trigger grouping together almost popped out. I had noticed it and pushed it back in. Nothing fell out of the trigger grouping.
Second, as I ran a tooth brush over this part, it started coming unscrewed... so I screwed it all the way back down with my fingers. Hopefully I didn't mess this up...
Finally, here are some mystery markings on my carbine:
B/R in a square
I also noticed my oiler is marked: SI
When I finally figured that out, I set the target up 30ish yards away and did my best. I never adjusted the sights or used carbine style iron sights for that matter! I'm pleased with my first time effort and things can only get better from here on!