An apparatus comprising: an optical device comprising a post extending from the optical device and a reference disposed on an outer surface of the optical device; and a knob rotatably connected to the optical device proximate the post and the reference, the knob comprising: a housing comprising a plurality of see-through portions; a gear pivotably disposed within the housing, wherein the gear comprises a ring engagement member and a receiver for receiving the post; and an inner ring disposed within the housing, wherein the inner ring is engaged with the ring engagement member, and wherein the inner ring comprises: a plurality of first indicia, each of the plurality of first indicia associated with a single specific first rotated position of the housing relative to the reference, wherein the plurality of first indicia are aligned with the plurality of see-through portions when the gear is in a first position; and a plurality of second indicia, each of the plurality of second indicia associated with a single specific second rotated position of the housing relative to the reference, wherein the plurality of second indicia are aligned with the plurality of see-through portions when the gear is in a second position. an optical device comprising a post extending from the optical device and a reference disposed on an outer surface of the optical device; and a knob rotatably connected to the optical device proximate the post and the reference, the knob comprising: a housing comprising a plurality of see-through portions; a gear pivotably disposed within the housing, wherein the gear comprises a ring engagement member and a receiver for receiving the post; and an inner ring disposed within the housing, wherein the inner ring is engaged with the ring engagement member, and wherein the inner ring comprises: a plurality of first indicia, each of the plurality of first indicia associated with a single specific first rotated position of the housing relative to the reference, wherein the plurality of first indicia are aligned with the plurality of see-through portions when the gear is in a first position; and a plurality of second indicia, each of the plurality of second indicia associated with a single specific second rotated position of the housing relative to the reference, wherein the plurality of second indicia are aligned with the plurality of see-through portions when the gear is in a second position. a housing comprising a plurality of see-through portions; a gear pivotably disposed within the housing, wherein the gear comprises a ring engagement member and a receiver for receiving the post; and an inner ring disposed within the housing, wherein the inner ring is engaged with the ring engagement member, and wherein the inner ring comprises: a plurality of first indicia, each of the plurality of first indicia associated with a single specific first rotated position of the housing relative to the reference, wherein the plurality of first indicia are aligned with the plurality of see-through portions when the gear is in a first position; and a plurality of second indicia, each of the plurality of second indicia associated with a single specific second rotated position of the housing relative to the reference, wherein the plurality of second indicia are aligned with the plurality of see-through portions when the gear is in a second position. a plurality of first indicia, each of the plurality of first indicia associated with a single specific first rotated position of the housing relative to the reference, wherein the plurality of first indicia are aligned with the plurality of see-through portions when the gear is in a first position; and a plurality of second indicia, each of the plurality of second indicia associated with a single specific second rotated position of the housing relative to the reference, wherein the plurality of second indicia are aligned with the plurality of see-through portions when the gear is in a second position.