I have a number of sets of "Midland supreme" 50/60's pannier sets. These don't include the bags but are the carriers that attach to the bike. I'm guessing they are for BSA's as I have one set in Silver, one in Devon red and two in Silver Beige.
I've no idea how you attach them, but the rear sections are drilled so I guess you fit them to the mudguards or other brackets. Anyway they are still in, what remains of, the old cardboard boxes. The base seems to fold up when a bag isn't fitted. All look in very good to good condition and are all brand new.
Any use?