Way back in the mists of time (last year) I was given a shed find gearbox for my Norton project, covered in a white corrosion, and seized up from years of neglect, it came to me for free, in case I could use it. Well of course I can, but it took a while to get it apart, everything was solid, the bearings rusted up, and some of the outer screws had been rounded off way back in the past. But I never gave up, I kept soaking it with penetrating oil, heating it with a heat gun, and a lot of perseverance, and finally a couple of weeks ago I got it all apart.
So I gave the cases to my friend James, and he waved a polishing mop at them, and gave them back this week, and next week it shall be rebuilt, with new bearings etc, ready to go back in the bike. It even has the correct numbers for my frames vintage.