Hint: Due to the high gm of the D3a, a conventional measurement with a tube tester is not possible. At least not meaningful.
Only a measurement in autobias mode is reliable

1 x  pair D3a Siemens tubes

3-mica quality

Can be used for any: 7721 5A/185K

Tested with RoeTest in triode mode:

Test result: gm = 27 + 25mA/V which is very strong

Random samples were taken for noise. No abnormalities