I have two Harry Quinn's - the frame numbers of my own bikes are Q2419 which the original owner says was 1966 and a later frame Q4948 whose owner purchased new in 1981.
If the period of 1945 to September 1977 inclusive is some 345 months this equates to approximately 12.2 frames per month on average and as Harry buil t personally until 1973 I assume the output would over twenty years evens out . Assuming no wild fluctuation in delivery, the market etc then my bike numbers fit loosely into the expected pattern with ± 1 year margin.
As I have not posted previously I apologise if all rules broken
Doug Branson LONDON UK