These are Duncan 3600 series
200 Ohm 3% 10 Turn Wire Wound Rotary Sensor / Potentiometers

.25% Linear Precision 
in a Double Ganged configuration on a common shaft
and a Vernier Dial 
Duncan Model 3600-898

This is TWO 200 ohm ten turn precision pots in one package

These vernier pots were recovered from ground based flight instrumentation test for a canceled project. The pots were sealed inside the two Martin Marietta avionics cabinets for the past two decades. 
Leads removed and tested.

Fully tested on an Agilent HP 4262A