Check this out - an original NBC glass slide for the 11-13-65 Jack Benny Hour with Bob Hope and The Beach Boys, on ebay!
http://www.ebay.com/itm/NBC-TV-PROMO-JA ... Sw4shX2W~E
This slide is from NBC affiliate WRC in Washington D.C. Usually, as one of these slides flashed on the screen for a few seconds, an announcer would say something like "This Sunday on NBC", "Tonight on NBC", "Next over most of these NBC stations", etc., etc.
Neat to see this on the internet... can't be many of these still around! - William