When did the Airsporter MK1lose it's adjustable sight and gain the flip up.
Not claiming great expertise, but I believe the really serious BSA researchers have identified various transitional examples that combine features of the Mk1 and early Mk2. IIRC, the Mk2 differed in the stock, barrel profile, machining of the front end of the cylinder, scope mount cuts, and rear sight, and probably other points of detail, so plenty of opportunities for transitional hybrids to have been made.
But, yes, basically the folding sight is supposed to be a Mk2 feature, along with the scope mount cuts (later grooves).
So the idea was you could flip down the sight if you mounted a scope?
Coincidentally I am preparing a piece on the first BSA telescope sights for Airgun World. I'm sorry to say my initial efforts at using them have been somewhat challenging, so I think I may just stick to the historical facts rather than including a practical test
Incidentally, as has been previously suggested, the flip up sight was initially a transitional feature first seen on GC and ED prefixed Airsporter/Club Mk 1 rifles, which were made in 1959, just before the Mark 1 became the Mark 2 and the Club was discontinued.
A review of the BSA Club, Airsporter Mk 1 and Mk 2 was written up in Airgun Shooter by Mike Jones and was published in the March, April and May 2016 issues of the magazine, which ought to answer some questions on these lovely old rifles. I'm not sure if they are on the Vintage Airgun Gallery but may be worth seeking out if not.
John M
As luck would have it, I have found a Mark 1, Mark 2, Mark 3 and Mark 4, some of which are still boxed. I plan to include images of all when I submit my review.
The Mark 1 does not have an Image Moving reticle, so to zero it, the crosshairs can end up anywhere but central in the tube, and the clarity is akin to looking through a milk bottle. Then there's the Mark 2, which was recommended for the BSA Merlin and has an Objective lens just a few mm wide!
All part of our history though and just goes to show how things have moved on in the space of just a few decades.
John