It has short plates with copper grid posts and a halo getter (I63 series). Tube tests as new with balanced sections and phono grade noise levels.
This 1974 Amperex 12AX7 / ECC83 tube has gray plates and a dimple disc getter.
The orange label has the Amperex globe logo and the Heerlen, Holland factory code is etched in the glass.
The 1965 Tung-Sol 12AX7A tubes in this precisely matched pair have long gray plates and halo getters.
The white labels on the glass have the Tung-Sol logo.
For the first part of the alpha code, the K designates a valve manufactured to specification K1001 or K1006; similarly a J designates a valve manufactured to a JAN or MIL spec.
The second letter of the first part of the alpha code describes the qualification approval the valve type has, a B denotes qualification by a UK authority, a U denotes US qualification, a D denotes Australian qualification and an X denotes Director of Electronics Research and Development (DERAD) approval.
They are labeled for Hammond organs and matching Heerlen, Holland factory codes are etched in the glass. This 1960s Amperex ECC83 / 12AX7 tube was made in Holland and labeled for organ, hi-fi audio, or medical companies. The white print on the glass has the Arcturus logo.
This tube appears new in box but it tests at about 80% for Gm on both sections. This Ei ECC83 / 12AX7 tube was made in pre-war Yugoslavia and labeled for other companies.
Valves used by the British military Armed Services were marked with a CV or common valve name which was defined by the Inter-Service Technical Valve Committee in 1941.
Often, below the CV number, a two part alpha code of the form KB/xx or JB/xx will be seen which gives the devices manufacturing specification and qualification .
The white print is labeled for Fisher or Dynaco (may be partial/missing). The 1963–64 Toshiba 12AX7A / ECC83 tubes in this precisely matched pair have short gray plates and halo getters. Excellent quality vintage 12AX7 tubes at an affordable price.