The 200CD is one of three oscillators that HP made many years ago. 
(The others were the Low Frequency Oscillator and the Wide Range 
Oscillator.) These are the ones with the 7" diameter chrome dial,
a Wein Bridge circuit that used pilot lights as the feedback loop,
and firebottles that produced many volts of output.

I've just acquired a pair of these venerable old beasts. 
The non-working one, SN 605, (owned by Crosley Radio at one point!)
needs help. I know I can likely buy a microfiche copy of the book 
from HP, but that costs.... and considering I paid a dollar for
the pair in the rain at the Dayton Hamvention;-}