I saw and answered this thread on the other forum as I saw it there first but just in case this is of interest to others...
Hi Stu,
You have what I consider the best of the early BSA telescope sights, the Mark III.
BSA announced their intent to narrow the scope dovetails on the Meteor and Airsporter to 11.5 mm in a circular letter sent to dealers and the Mark III was intended to fit these narrower dovetails. It was to be made available from the end of November 1965.
The sight was still included in a 1969 BSA flyer but omitted from a 1970 dated flyer, so had relatively short production life.
It was well made of metal and I believe British made too. Just the thing for an Airsporter Mk 2 with 11.5mm scope dovetails.
Kind regards,
John M
Currently looking for Baikal Makarov pistols with the following prefixes to the serial number: 98, T01, T09, T21, T22
Prefer boxed or cased but will consider loose examples too.