From motorbike mechanic to doctor eh? I suppose fix one, fix all. At least it's better than being a barber and also amputating the odd limb or so, as in chop a hair or a limb, all in a day's work.

Right having dispensed with the sick humour (heh heh pun intended), on to the real stuff.

I'm going to call the Speed D3. I don't know what make 3-speed is installed, but generally they are very reliable. Derailers aren't very complex OTOH, but require a lot more babying to keep them running perfectly. Especially cleaning in poor weather. A 3-speed's chain can be run with zero oil, as our in-house dry chain fanatic, ol' Chucky, will testify.