Here is a clue. You'll need to follow up on it.

http://www.deactivated-guns.co.uk/live-f.../prod_5002.html

Here is another. http://www.deactivated-guns.co.uk/live-f.../prod_5002.html

Here is a link to an old discussion on BSA.

http://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=364129&page=1

Also, Boxlocks and Sidelocks by Boothroyd has a short history of the Company.

I own one and still like it. My only complaint is that it is wide at the breech because of the dovetail lumps. Being wide it sometimes feels top heavy, but is very controllable. It was my first double 30 years ago and can't let go of it.