This vacuum tube is one of many items I received upon the retirement (end-of-life preparations) of someone who used to work as a professional in the field of acoustics and communications. (I purchased it.) I have absolutely no knowledge of vacuum tubes, and frankly, I didn't need them. However, I couldn't refuse the offer to buy a collection of items, so I ended up purchasing everything. But, I haven't even used them, and I don't even know how to check if they work, so I've decided to sell them to someone who needs them. Even though it was a request from someone I'm indebted to, I regret buying something I didn't need, especially since I paid for it. I was told that this vacuum tube was "brand new and unused" when I received it, and the original bag appears to be sealed, with no signs of it being opened. Indeed, it seems to be unused. A piece of thick paper with what appears to be the part number is sealed in the header of the bag, and although it's difficult to see in the image, it says "V1 2B52". (Please refer to the last image.) Because it's unopened, the printing on the vacuum tube itself is still clear, as it hasn't been touched. However, the needle-like electrodes (?) appear to be slightly tarnished. I am only selling the vacuum tube (1 piece) shown in the image. I don't know how to check if it works, so it has been kept unopened since I received it, and I don't know if it can actually be used. You may want to consider it as a junk item. I have selected "brand new and unused" for the product condition, but please consider purchasing only if you understand that it is a "vacuum tube that has not been tested and may be considered a junk item." We cannot offer any support for returns, refunds, or exchanges. Also, we would appreciate it if you could understand that we will use recycled packaging materials when shipping the product. (We plan to ship via Takkyubin Compact.) Due to work, it may take some time to respond to messages and ship the item. If you are in a hurry, please refrain from purchasing. (I will do my best to respond quickly.) Thank you for your understanding.