A Jenkins Prismatic disc (1924) sold this afternoon on ebay along with a neon tube etc. The prismatic disc is on the ebay auction 4th and 6th picture.

http://www.ebay.com/itm/PRE-1935-TELEVISION-PARTS-JENKINS-NEON-TUBE-ANTIQUE-PATENT-SCHEMATICS-/322383235598?_trksid=p2047675.l2557&ssPageName=STRK%3AMEBIDX%3AIT&nma=true&si=cvIFpQtd5tIQTyn6cBclPeDLzj0%253D&orig_cvip=true&rt=nc

A set of prismatic discs below which are displayed at the Henry Ford Museum.

http://www.madehow.com/images/hpm_0000_0003_0_img0173.jpg

I don't know if I'll ever make it to the Ford Museum so I may never see one live.