thank you Ernesto. I just use my finger to simulate having film passing through the sprocket. The shutter cocks and fires, and looking through the lens, it looks like it needs a good clean or may even have living organisms.
Would using rubbing alcohol with a q tip be a good start on the external surface of the glass? Thank you! From Ming
PS I attached a cable release, opened the shutter at B, and was a bit disappointed to see that the glass looks like a Petrie dish from my school days. Sigh ... Oh, I already put some isocol on both the external surfaces (front and back) and the patterns are there, certainly not dust.