Format is CV followed by up to 5 digits, e.g. CV4003. 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, 5960-99-000-4003 = CV4003 (12AU7WA), with 99 indicating country of origin as UK.
