Thanks for all the comments

Dean - I wish I could do work at that scale..... unfortunately, my eyes just aren't up to it these days, and IMHO my lathe doesn't spin fast enough to do really intricate tiny work, at 670rpm, by the time you get down to turning a couple of mm, it's more likely to bend than cut... One day, a smaller and much faster lathe will be on my shopping list.... unless I can get the Mazak CNC going, I think that's capable of a couple of thousand RPM.
So anyway, in lieu of references, the knob is approx 34mm OD, the mounting shaft is 6mm (+ a bit of error in the drill bit). I didn't quite get it perfectly trued when I cut off the front face, which a close inspection will reveal; and for some reason the ball-end cutter that I cut the flutes with left a fairly bumpy finish. I may try a different technique next time I make a knob (plunge cut with a straight cutter, but only removing the same sort of amount of arc.
Hanermo - you're right, it's not polished... at least, not completely. It spent a few moments under a brass wire wheel, until I got fed up of bits of brass hitting me in the face.... then it spent a few minutes under a cotton polishing mop, with whatever polish was left over from a previous job. The only polishing gear I have is a small pot of Meguiar's "Metal Polysh" and some rags (when I can find them)...
One day, I will polish a knob to the point you can see your face in it...... erm, did I say that out loud?
