Thanks very much indeed, mine at 621*** places it in the 3rd or 4th qtr 1960 which is what I thought.
Yes you are correct my original dial is a "swiss" only gloss black, gilt dial with chapter ring, and SCOC wording.
In the early 90's I had the dial and hands (small 24hr arrow head pointer) replaced with service ones but thankfully asked for the return of the originals. I only changed them as the dials trithim was marked with brown spots, I intend to take a photo of this and post it on this fourm in the near future in the hope that someone has a cure, as I would like to have it replaced at some time.
I do love these vintage 1675's and 5513's, after my dialy fix of this site for the past 2years this is my first post, thanks again for your response.