Maker name of potentiometers?

[N_Cook]

1960s made in England equipment
Distinctive brownish/orangeish/pinkish colour, high temp plastic track
carrier rather than usual phenolic board. No maker mark but stamped on the
steel shield is 250, presumably type number for log, and 270 for semi-log
ones. Other distinctive features is the 3 rivets are copper rather than
coppery coated aluminium and the anti-rotation lug is a moulded part of
this plastic . Plastic probably mineral filled and will puncture ,but not
melt noticeably, with pushing the point of a soldering iron into it.

 

[N_Cook]

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%20images/Parts%20N%20Such/Morganite%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