The CV137 is a miniature diode triode and the prototype was the Mullard EAC91. Note that unlike most diode triode combinations the diode has a separate cathode.
The design function was as a triode oscillator and frequency changer operating at up to 300 MHz. The proposed circuit is included on the data-sheet.
The maker name and Made in West Germany. The triode section is on the left and the independent diode is on the right.
The heater wire was coiled before the ceramic coating was applied.
The thin glass tube envelope is 18 mm in diameter, and excluding the B7G base pins is 46 mm tall.
Reference: Data-sheet. Type CV137 was first introduced in 1947. See also1947 adverts.
