I've done some research on the web and through the USLHS. There's an article in the MAY edition of HARBOUR NEWS, the bimonthly newsletter of the North Georgia Beacon Brigade - here's a link to the website
http://www.ngbb.org/

Go to the NEWSLETTER page and the May edition. There are some pictures showing a few variations, including a Portuguese lens with a special panel used as an aerobeacon.
Anne