I have a quad of these tubes - the box says 6n3cE, but in translation they are 6P3S-E according to the label from my vendor. Late 70's early 80's vintage I think.
Mine come from Jim McShane who labels the tube boxes. There are individual measures per tube, but printed are the following:
Vp: 465 volts Vg2: 465 volts V bias: -50 volts.
I don't have a lot of electrical knowledge, and can just pass on what I see.
Each tube has a spec sheet, however it is in Russian. If you want, pm me and I can try and photograph or scan these and then email you.
If you are buying some out of Russia or the Ukraine I would recommend getting more than you need to get better chances of nicely matched pairs etc. I preferred to get mine from Jim at what I felt was a good price.
In my amp (Cayin A-60t) they give the best bass, clean mids and highs. I really like them. I have also corresponded with another user who employed them in a guitar amp who had the opposite experience and replaced them.
So I guess it depends on what you are using them in, and what your preferences are. No doubt they are a sturdy tube, but have a coin base that makes extracting a little more difficult than those with a thick base.
Heading downstairs to use them right now !