Bell & Howell made film projectors and were regarded as one of the finest makes. Like other high volume customers the valve supplier has marked the valve as being from Bell & Howell.
The 6F6G output pentode was designed for audio amplification in radio receivers. The operating values given are for single ended use with an anode load of 7,000 Ω.
If a pair are used as an audio amplifier in push pull class A, 10.5 Watts are possible with 3% distortion.
The equivalent type KT63 is a beam tetrode. Type 42E is electrically the same but with a UX6 base. Additionally the 7D5 is a 6F6G with a 0.315 Amp 13 Volt heater and a B7 Base cap.
The Bell & Howell name on the base cap. The envelope has the Type designation within an octagon border - too feint to be seen here.
The top mica with the U shaped heat sink fitted to the copper control grid supports.
The classic envelope is 44 mm in diameter and excluding the IO base pins the length is103 mm.
References: Data-sheet, 1040 & 1043. Type 6F6G was first introduced in 1937. See also1937 adverts.