Sylvania was the developer of the Loktal tubes, which were a rebuttal to RCA's metal tubes. They were introduced around 1939, and quickly became adopted by Colonial, Philco and Zenith; the three manufacturers who were unwilling to use the metal tubes, and pay royalties to RCA for using them. All three had close ties to Sylvania as an OEM tube supplier.
RCA wasted no time in firing back with the all-glass miniature tubes, just as WWII was about to start. The Loktal tubes hung around for a few years after the war, but were pretty much obsolete by the early 1950s.
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