I have a lot of RCA 6AS7G tubes and only was noisy. Are you buying them on ebay only ?
I can't agree the RCA's are noisy, like it's been said above, I think you just were unlucky
Can't you just order via the web in a brick and mortar shop? Or here on head-fi in the for sale/trade forums? Nothing's ever a sure thing but Ebay is always a gamble although I only got ripped off once, with 2 Thomson tubes that looked pristine but were in fact totally exhausted. And one Chatham 2399 that's noisy but I got 4 at a very decent price so on balance it was still an ok deal.
This Tung-Sol looks very much like an RCA to my eyes: steel grid posts, metal shields below the bottom mica, a single D-getter, and even the 8-sided polyhedron on the glass with a small gap in the outline, which some say can be used to date RCA tubes.
But of course, this is just my best guess.....
When you say "both types", do you mean both the 6N13S and the 6N5S?
I am for sure the winged C 6N13S is a bit of a bargain imo compared to the RCA ,Sylvania, 6as7g and recently I have bee hearing good things about the 6N13P Dawn Star which I have yet to try.
My new Feliks-Audio Elise that I have just received uses the 6N13S, and I must admit I'm already VERY impressed with them. Am looking forward to seeing just how they compare to the GEC CV2523s...