I have been tube rolling all of the 12au7 tubes from my tube stash.

Note: I am still using the two Sovtek 12ax7's (from Decware) in the ZP3.

The winner is a Mystery Tube (12au7A), it looks like a NOS RFT (East Germany). Great detail and great bass  (it is also smooth).

It is marked in bright RED 12AX7A/ECC82.

The next line is hard to read (see photo).

Made in E Germany?


The tubes are Grey Plate, Short Plate (or square), Smooth Plate.

Halo or circle getter with one support (from a large post, see photo)

A clear round circle on the glass bottom.

Inside the round circle is a V and a mirror image of "12" (under the V).



My second choice, but not close second, is the RCA Command 5814a


Peter

I found a better 12au7.

Thanks to Brent Jessee.

It is smoother than the RFT 12au7 pictured above.

It is a 12au7 Mazda greyplate, 1960s, made in France

From Brent Jessee:

New old stock, original and white Box. Grey plates, very similar to the very rare Mazda silver plate tubes. These are also hard to find in the USA. Excellent, 1960s vintage long lived 12AU7 types with the distinct European vintage flavor that a modern tube just cannot capture! These have the sweetness and dynamic punch typical of Mazda


Try tube rolling the 12au7, it makes a big difference in the sound.

My result:

Higher resolution and detail

Bass punch (a big difference)

Livelier

and Smoooth.