[rif]

It's a 6H8C.  Looks like III-79 could be a date code?  I really dont know much about tubes.  Can you tell who the mfg is?  On the glass, there's a pentagon. On the black base, there's a rhombus with an O in it.  And a pill shape outline with OTK.

I'm assuming Russian and those are Cyrillic characters.

Picture attached.

Thanks!

[FullRangeMan]

Tube is 6SN7 made by Novosibirsk(old logo) in Novosibirsk city,Russia, date is March 1979, OTK is factory QC approved, Diamond is military approved.

6H8C Novosibirsk collective factory is a rare tube today in the west.

[JohnR]

[Cross-posted with FRM]

I believe that's the "Russian 6SN7" e.g.

http://www.cryoset.com/catalog/product_info.php?products_id=337

[rif]

Thanks for the quick reply!  Is it any good in your opinion?  Rare russian tube sounds great, but probably means little to the sound.  I'm using a tungsol now.

Reminds me of a car joke.  A certain make/ model sold so poorly that almost now one owned one.  But they could brag about it being more exclusive them a BMW 5 series.  (new smileys!)

[FullRangeMan]

I was about to ask about the sound of this model.

[JohnR]

Is it any good in your opinion?

If you're asking me (?) - sorry I have no idea

[Rusty Jefferson]

I use the Melz metal base 6h8c in my preamp and they're excellent. Hard to get quiet well matched pairs at a reasonable price, though. Not better than the Sylvanias or RCAs, but competitive imo. Never tried your brand. Please post your thoughts, especially if you try others.

[DaveC113]

It's been years since I tried the plastic base 6H8C, they were less refined vs most others if I remember correctly.

Like Rusty I do use the metal-base version which are very different vs the plastic base tube and are excellent. There are many variations though, with the hole-plate 1578-marked tubes being the best according to many, but I've also heard the black-plate version without holes are even better, this is what I use and I think they are better vs most other NOS 6SN7 types. I also use the 6SL7 version, the 6H9C metal-base black-plate tubes and they are also excellent. I'm not willing to spend the $200+/pair price for the holey-plates. You can usually find the black non-holey plates for under $100/pair.

[A_shah]

I was about to ask about the sound of this model.

@fullrangeman
can you identify these for me ?  the claim is Sylvania VT-231 dated 1966 ?
Asghar

[FullRangeMan]

Sorry I cant, but date is SET1966, plate looks similar to this TungSol tall boy, but not the mica spacers:

Sure its not a Russian, it may be the brand you mentioned.
This thread may help: https://www.head-fi.org/threads/the-6sn7-identification-guide.209782/

[A_shah]

 Thanks !