From Lighthouser:
1) The lens is constantly white, when lit, with a bright flash every 30 seconds, but what makes this lens unique is that the midsection of the lens where the bull's-eyes are located rotates, while the upper and lower thirds of the lens stay motionless.
Most of your information is included in the full size PDF page, Judy. But where did you get the above? I don't think that is correct.
The mechanics of doing that would be very difficult. The entire lens is sitting on the pedestal which rotates on 'chariot wheels'.
In some other lenses with 'bulls-eye' panels, the prisms above and below the midpoint are curved to match the round shape of the bulls-eye panels.
See the Official Collectors Guide, pages 390-399.
