one suggestion - where you describe "Stainless Steel was just making its advent, and was a difficult material for the metal working machines that the watch manufacturers used. New machines had to be invented, and it was, from a manufacturing point of view, a challenge" - i suspect it was not the machinery but the alloy that needed development. Later SS alloys were developed that contained a slight bit of lead (316L) that made it easier to turn and cut - the lead serves as a lubricant for the cutting bit