Replacing the x50 objective lens:

Part Number: 344-89964-40  Objective lens x50

If the objective lens is damaged or the lens visibility is deteriorated due to dust on the lens surface or corrosion, replace the lens.
Remove the old lens by turning it with your fingers, and mount a new lens. After the x50 objective lens is replaced, adjust the focal point by turning the adjustment ring, and perform the magnification adjustment and indentation centering procedures.