I have a question please. If a valve is sold as NOS but the glass near the top is dark and smoky on the inside is it likely it had been used? I'm assuming this is coming from the heaters and possibly the electrons being emitted over time. In particular is it more likely if you have a pair, one clear and the other smoky? I'm thinking here some production processes might smoke the glass but then surely they should all be smoky? Not black but clearly darker when you hold them to the light, or against white paper.
It happened the other week off ebay and I sent it back but this time it's a private sale. I don't want to raise the issue unless it's clearly (or at least in the balance of probability) not NOS.
Once this questions been answered this thread could be used for other tips about spotting NOS (or not) valves.
Thanks
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