`''  :: Thanks for the pointers. I found that lens turrets are most commonly found in the context of microscopes, and there's no mention in the Optical microscope article. One also finds a similar mechanism in machining, to swap tool bits such as drills. I haven't yet found a mention of this usage in the Metalworking articles. including CNC.    == Gallery == : I don't think the images ``Turrets at Donaldson's College, Edinburgh, Scotland`` or ``Turret atop Havant dental surgery`` should be provided as examples because, per the article, these would be considered towers not turrets because they extend to the ground.`