Update,
After a bit of a hiatus, I thought I would put an end to speculation about this hub.
What I have is a A65 two-leading 68ish hub with a one-off sleeve, 20mm on the OD, Imp. bore, to fit the metric hub bearings.
The sleeve was bored to accept the A/B 7" hub spindle, thus fitting the said forks. Can't make up my mind, was the sleeve b/plate retainer nut thread cut before boring, sleeve wall about 45 thou thick, or was it cut after, with very fine cuts. I'd go for the former. Anyway, thats what it is.
Not being a BSA/Triumph person, I thought I had some sort of intermediate hub, with the slot to mate with the later fork leg, AND a boss with a stud to accept the earlier leg brake torque stay. And the bearing sleeve to convert, of course. On washing and a closer inspection, the boss had been grafted on, welded (in quotemarks) to built it up, drilled and tapped. I cut and ground it off, and talk about a wing and a prayer. No penetration, just hanging on and no more. Gas, I would think.
Incidentally, some Vincents, 1951 build, during the Korean war, my how the World turns, seem to have heard that name lately, did the same. Bearing shortages, metric bearings, metric to Imp. sleeve. That cost me a few hours one time. Ho Ho.
So puzzle solved.
Regards to all who commented, Ken.