The only things we know about this exhibit come from the printing on the metallised envelope of this imported valve. It is clearly a vari-μ tetrode for RF amplification in broadcast receivers designed for use on AC mains. The screw top cap places the date to the early 1930s.
The reverse is plain.
The balloon envelope is 50 mm in diameter and, excluding the B5 base pins, is 127 mm tall.
Absolute Maximum Operating Conditions¶
Updated March 04, 2022.