The 6S4P-EV (6C4П-EB) is a HF triode with low level of intrinsic noises. Military -EV version, long life (> 5000 hrs) and high durability. Made for military. 6S4P-EV is similar to the EC86/PC86 tubes and very close to WE417A too, but is has a different pinout. New old stock tubes. Made in the end of 70's and early 80's (please see the gallery).