amperex 6922 pq white label tubes

Then there’s the E188CC, E88CC, ECC88, CCa.
All the companies and countries where each were made,
plus all the changes to each over the years etc.

I would hold off on buying expensive tubes until you familiarize yourself with the variables, OR get advice from someone who knows the subject.
Save yourself from expensive mistakes and/or getting ripped-off.

My current favorite is the late 1950s "Made in Holland" Amperex E188CC (European 7308) with D-foil getter. Really outstanding but they are pricey.
Last pair I bought from Brent Jesse, another excellent source who extensively tests his tubes.

The earlier "Made in Holland" E88CC (European 6922) with large halo getters are also excellent although some folks prefer the "Made In USA" Amperex 6922 and 7308 tubes. IMO: If tested thoroughly and bought from a reputable dealer you can’t go wrong with any of them.

BTW: There are some good tube dealers on ebay but how do you figure out who they are?