Jim Cross writes: "The National Union Radio Corporation was formed by the merger of Sonatron, Magnatron, Televocal, and Northern Manufacturing (Marathon brand) in August 1929 for the specific purpose of making receiving tubes. The name was changed to the National Union Electric Corporation in May 1954. ... NU made receiving tubes up into the late 1950s, and continued to make odd special purpose types up to at least 1968, when they registered their last type (type 8632)."
National Union 193- Type 2005 Videotron - Data and application notes for a 5" CRT intended for television use. Includes a schematic of a television receiver (without sound section). No date but likely 1938 or 1939.
National Union 193- Type 2203 Monotron - Data and application notes for a 3" monoscope - a CRT that generates a fixed test pattern. Includes a schematic of a test pattern generator using the 2203. No date but likely 1938 or 1939.