This is a PM-brand 12AX7LM vacuum tube. For pre-amplification / dual triode / low noise / low microphonics. It's said to be ideal for those who want a clearer sound. I purchased it about 10 years ago as a replacement for amplifiers and effectors that use vacuum tubes. I've used it a few times as a replacement, but I haven't used it permanently for years at a time. After that, due to the advancement of digital technology, I had no opportunity to use it and have been storing it.