The 6CM4 was designed for use as a grounded grid amplifier, oscillator or mixer for UHF television receiver front ends between 430 and 860 MHz. Hewlett Packard were top quality test instrument makers and this valve would be used in such a role.
In 1999 the instrument business of Hewlett Packard was renamed Agilent and remains one of the most respected names in test equipment.
This exhibit was made in West Germany by Amperex.
The actual triode element is a small part of the envelope space. As a professional valve the pins are gold plated for minimum contact resistance and avoidance of long term change due to corrosion.
The thin glass tube envelope is 20 mm in diameter, and excluding the B9A base pins is 48 mm tall.