Got a stash of these a while back. They are the military version of the 12AU7. I really like these tubes for making a loud amp quieter and taming some high end spikyness. Just wanted to post this for those that might want to try it. I have a 67 Bassman that is a little on the loud/hard side and has just a tinge of harshness in the high end with the Emi Speaker I paired it with. Not bad mind you but it just needed something to settle it down and smooth it out. I stuck a 5814 Raytheon Black Plate in V1 and V3 and a Mullard ECC83 in V2 with an RCA 6201 in V3. The power section has a set of new =C= 6L6's in it. This combination took this thing down a huge notch and let me Crank it for a softer more pleasent sound. Jumpering the Channels with both Volumes dimed yielded a much user friendly Volume and Tone to my sound with this Amp.