CV designation system

For example: CV4004
   Base format is 'Cvxxxx', where xxxx is an 4 digits number as type code. This designation has used by the British Military to codify vacuum tubes, gas tubes, and latterly, some semiconductor devices.
CV numbers can be directly mapped onto NATO numbers, as 5960-XX-000-YYYY where XX is the country code, and YYYY is the CV number. For example, 5960-99-000-4004=CV4004 (12AX7WA), with 99 indicating country of origin as UK.