I have quite few years of Rolling 6SN7's where only Half Tube is required in the circuit.
I have used tubes from the 1940's - 50's - 60's - 70's up to ones bought New Stock a Few Years passed.
Tungsol and EH and a Russian equivalent is also classed as a New Stock anf have been used.
Most recently the Mullard ECC 32 has been appointed a Valve to be a drop in replacement.
In my system I have got my preferred Valves, but have no issues with using New Valves.
The Russian Equivalent lasted about an hour and is binned, no longer to be used.
That Rusky Critter was not to be sold to anybody as a Valve for a Amp.
There is a Linlai Elite Thread on the Gon, that offers very interesting assessments of experiences had with this Valve. I see as a Valve of Interest.
Do Note: 6SN7 as a Valve is a challenge to find ones that are not noisy, they can't hide from those who know how to find them.
Sellers typically don't have a discussion about noise in Valves only measurements are the reported info.
High Percentage of Usage Life Valves does not create a quiet Valve
All Valves retained by myself are on par with Manufacturers recommend measurements and are deftly quiet until they are not, non deftly quiet Valves are able to measure in a way that makes them very attractive as a Valve.
Spares not only 6SN7's that a correctly measured and deftly quiet are expensive to have as a safeguard, but are a mandatory idling component for my system.
Luckily an idling Valve can substantially appreciate in Value.