Rolleiflex Old Standard Model 621(Type 1) 1932-34

Came with a lovely bespoke leather case. Tried to take the viewfinder off to clean it up a little bit. The screws are brass (i think) and won't budge. I don't want to strip them. Any suggestions welcome. There's a slight scratch on the front glass of the viewfinder and as you can see this has been used but what djah expect for a 70 year old camera!!!

Done