The P&L condenser has three stacked lenses. Controls are for X and Y centering (A, B) and for rotation (C). There is no inserted Nicol polarizer, although the rotation control suggests that one was included.
X and Y movement of the condenser is effected by thumbscrew controlled mechanism.
This thumbwheel integrates the 9-position aperture control (top wheel showing) and the 4-position darkfield stops (bottom wheel showing).
Example darkfield stop in place.