TV Screen Magnifying Lens
In the late 1940s and early 1950s, when TV picture tube sizes were a tiny 3", 5", 7", 10" and 12", there were several companies that marketed TV screen magnifying lens, to enlarge the viewable image size. They were either attached to the face of the set, or were mounted on a bracket that allowed the lens to sit directly in front of the picture tube. Some were mounted on elaborate adjustable floor stands, while others 'hung' off the top of the TV set cabinet. It is also interesting to note that they came in various colors, like aqua blue, yellows, reds and greens -- depending on what image shade & color might visually appeal to viewers.
Most lens were usually made of plastic or Plexiglass, and some were filled with a clear liquid (either oil or water). The largest size was in the 16" to 17" range. A few TV sets had the magnifiers built right into the cabinet, or permanently mounted on the face of the picture tube.
Examples on this site:
1948 14" TECO or
1948 7" Temple; Picture tube mounted, or
projection TV set lens.
There were also various types of filters that could be applied to the face of the picture tube. These filters promised greater clarity with the reduction of glare from reflected light. One filter claimed to convert your black & white TV set to color (this was a gimmick). You simply applied the color filter to your TV screen, and the three translucent horizontal bands of color would visually simulate color television (with blue at the top to simulate sky scenes, for example).