With a light in just the right direction (downside of circular inspection
lamp lights) I just managed to see a faded name on the external face of
the plastic plate, Morganite England 62 presumably 1962

black version, apparently showing the same plastic but black anti-rotation
lug
http://www.zenn.com.sg/Marketplace%2...organite%20pot
entiometer.JPG

Apparently there is a mineral Morganite , something like the colour of this
plastic , deliberate?
Cannot find a www pic of this Morganite distinctive pink/brown/orange form,
so looks as though I'll have to take a pic for posterity