question, does the metal cap at the back come off? and is there any adjustments in that?

I would be a little hesitant and want to see if someone has made a venture into something like this before. I also notice there are little "Arms" around the tube. I don't want to touch them right now, but can they be used for calibration. To give you an idea what these "Arms" look like, if you look at the neck of the tube, you see the flat things going down to the rings that go around the tube. I am not sure what they are for, but I am wondering if they can be used to control various parts of it.