My bad I was given some misinformation and here are a few corrections....I have no idea why Arcturus produced tubes using optical blue glass starting their production in 1927!..Back then the only units using them were those wooden cathedral style radios and such and you could not even see the glow of the tubes with the wooden case....It is believed blue glass tubes were being phased out by 1933, probably remaindered stocks. That makes these tubes truly very very rare: both because of age and because why pay more for a tube you would never really see. These are a pair and the plate construction matches, with a O embossed in the center of the plate. I have seen some with the ladder type embossing. They have engraved bases of course. For some reason compared to other 45's I have the Arcturus blues have the most pristine sound. I do not know why, maybe its psychological with that cool,blue glass. Used of course, tested good, Some scratches on base from tube retainers (hey they date back to 1930 !) Arcturus was seemingly set up as a premium tube company. Construction is quite even and bases are very tight. I have several NFG samples too, BTW. Arcturus was not without their issues. Still tubes of that era seem to have large bright getter flash and some nice build cnstruction
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