The EA52 disc seal UHF diode dates from 1950. The cathode is the 15mm diameter annular ring and the anode is the end spike.
This valve was designed for use in UHF voltmeter and monitoring devices and operate at up to 1 GHz.
The makers name and within the coiled heater.
The glass carries the fact that this exhibit was made in Germany. The red spot marks the anode connection.
The external connections to the heater are gold plated and this valve was designed to be wired-in. Note the red plat (copper clad Dumet) metal forming the glass to metal seal that the golds plated wires attach to.
Thanks to Richard Oakley for donating this exhibit.
The thin glass tube envelope is 11 mm in diameter and, excluding the base pins, is 38 mm tall.
Reference: Datasheet. Type EA52 was first introduced in 1950.