On the "P" , I had a first year (1932) Superposed that had a "p" after the serial number, when I was collecting pre-war Superposes about 15 years ago. I had about a dozen of them and only one had the "P". I did a lot of research on this, and never could find the answer. A lot of guessing, but nothing concrete!
If you find a creditable answer, I am sure a lot of people would be interested. A gold "S" uner the safety is a yes.
Good luck, Herb

"In my GSP I do trust"