Neil,
I had not thought about different manufacturers making the clasps and I don't know how many different manufacturers were contracted. Do you have any information on this? Given the volume of orders, I could imagine that multiple companies may have been employed.
Dies for the QSA have appeared on the market from time to time but I have never seen any clasp dies. If multiple manufacturers were used, perhaps they were issued with official clasp dies to ensure uniformity of manufacture? This would keep any variation between clasps to a minimum.
That said, my experience has been that the face of official clasps is very uniform to the extent that slight deviation usually indicates a copy.
Some variation in the width of the lugs is visible on QSAs and the manual and official process of riveting clasps together does not always end with neatly aligned clasps or lugs but this is rare in my experience.
