Once again we are getting our knockers in a knot over something that can never be resolved.
On a 1962 A10 SR what controls came on it from the factory?
Answer;-
Whatever parts that were in stock on that dayThere are several different "correct" parts.
1) those shown in advertising photos which could have been taken any time from 2 years before the model was made to one year after.
2) those shown on the parts book which is
what was intended to fit and might not necessarily be identical to the drawing in the book or what was actually fitted to production bikes.
3) what was actually fitted to the bike at the factory on the day the bike was made. The production line @Birmingham never stopped so if the "correct" parts were not available the bike got fitted with whatever was available at that time. Some times the factory sent the "correct" replacement parts to the dealers to swap and some times they didn't
4) what was on the bike the day it crossed the threshold of the dealers show rooms.
Now as for Roy ( expert on every thing with wheels on it ) Bacon.
He was just a journo who kept all of the bumph that every maker or importer sent to the publisher that he worked for. In retirement he compiled all of the advertising literature into a roughly chronological order and published his first ( twins & tripples I think ) which has ( from memory ) 9 incorrectly captioned photos, none of which were corrected in the second, third or fourth editions. He then did the same thing with Triumph, Norton & Vincient twins.
Osprey ( the original publishers ) and Roy realized that they were on a winner, filing up a void and there was a good market for these types of books. And the same format was applied to around 70 books.
Now I have nothing personal against Roy with the exception that he dose not divulge that his primary reference material is factory promotional literature and he writes as if he has a deep & personnal knowledge of the material ( which he has not ). ( Nortons excepted)
Once the format was set subbies were employed to compile all of his available material into a publishable state.
As general historical reading on BSA his books are good but as a factual reference they should be treated with caution. They were written using the same material as the motorcycle magazines of the time ( and we know how accurate that was ). If you area BSA freak like myself then you end up with a lot of original factory material and when you do it becomes glaringly obvious where he sourced his material from and in particular most of the photos & illustrations.