An optical device has a post and a reference. A knob is rotatably connected to the optical device and has see-though portions and a gear pivotably disposed therein. The gear has a ring engagement member and a receiver for receiving the post and an inner ring is disposed within the housing. The inner ring includes a first indicia and second indicia. The first indicia are aligned with the plurality of see-through portions when the gear is in a first position. The second indicia are aligned with the plurality of see-through portions when the gear is in a second position. Each of the first and second indicia is associated with a single specific rotated position of the housing relative to the reference.