Screws A hold the focussing thumbscrew body to the main body. Screws B are red - and this should immediately tell you something. Yep......., red = desiccation screw into the OG housing. You won't damage anything per-se as it's all mechanical and optical operation in the OG system (as opposed to electronic). You will need to take extreme care to clean the lenses in a dust free and dry room.

I say no more.............. except that I hope noone else in the universe is thinking of trying to adjust the focus using the OG lens housing