Made in Russia. A great tube at a great price. Given that small tubes like this last typically between 5,000 and 10,000 hours, it may make sense to spend just a little more and get the vintage Mullard CV4024 made in Great Britain. That tube is selling at a low price right now and will be $150 each at some point.
Platinum grade - The best of the best. Lowest noise and microphony with the tightest triode balance we have available. This is typically 10% or tighter, but may be higher depending on available stock.
Gold grade - Low noise and microphonics with a triode balance typically between 15% and 20%, but may be higher depending on available stock.
Driver/Buffer grade - Lowest noise but not the lowest in microphony. Triode balance will be similar to Gold grade.
This grade is only suitable for use in the driver stage of an amplifier, or the output/buffer stage of a DAC or CD Player.
If you have a preamp or phonostage, you need at least Gold grade.