Re:
'221186' looks suspiciously like a date-stamp to me; i.e. 22nd November 1986.
A lot can happen to a frame in forty years..
I got a new bracket shell put in my '75 'mystery' frame (which does happen to have a 5-digit 'first two digits=year' serial number with a zero in third position) around the turn of the millenium.
I took the bare frame, minus forks, to a long-established North London lightweight shop, discussed options with the guy in there, and left the frame with him. It was a good few months before I got a phone call telling me my frame was ready to pick up. I've no idea who actually did the work, but they did a fine job, and I know that because the shell they were replacing had itself been a replacement shell from a few years before (in another city) that had been put in badly- so far out of alignment as to be unrideable if you valued your knees at all.
Anyway the point is that on neither occasion of BB shell replacement was anything stamped on the new BB shell. I guess the first 'replacer' had the option of stamping the new shell with the old number, since it was there in plain sight on the original shell he was replacing. The second 'replacer' didn't have the option, since the original number was gone, and now only existed on the fork steerer, and the forks were still with me.
I actually have an inherited set of those number stamps myself, so if I chose to, I could stamp the original number, or
any number, back into the BB shell.
So.. you know.. in that situation I wonder what the established frame builder etiquette might be? I can't be the only person who has had to get a BB shell replaced, although I am probably among a smaller number of people who've had to get one replaced twice in as many years...
another point to clarify. This frame despite questions, remains the ONLY "69" frame number that also has any kind of date attached to it supporting the theory that "69 Shop series" stretched from '69 to '74 +/-'75.
Agreed... moreover it is getting rarer to find these forty year-old machines still with their original owner/commissioner, who presumably knows the whole story of their bike- what it had done to it when, and what it was like before it was done..