All good fun Swarfy. A nice diversion for anoraks!
I'll stick with a B though - footrest in right place for them too (but not sure about gusset or scrap-iron bit in rear triangle of frame). Unfinned bit at barrel base, exh port about right, magdyn, etc etc, nothing shouts 'Not B' from what I can see fromtrying to compare with pic here.
Who knows - but not THAT many teles + rigid to choose from if it was made like that, and it def isn't an early-tele-adopting Matchless. I think Ariels had plungers or Anstey wotsits by the time they had teles, but it's nigh on 50 years since I had an Ariel of my very own and was 'into' them a bit.
Or maybe it's a bitza-mixture.