Tyne lists about 250 US brands for vacuum tubes in "The Saga of the Vacuum Tube" but not Star-Ko. Since Star-Ko praises that the tube was produced "in tremendous quantities" and sells the X245 for $ 1.69 in quantities with a list price of $ 3.50 we think that Star-Ko bought tubes with lower quality from a big tube maker to sell them off. Or they could sell at a time where the tube was already obsolete. See also Y-224. Found in the "Neonlite" brand also. No information available.
