This double triode carries the Bell & Howell label. Bell & Howell made equipment, especially small film projectors for 16 mm cine film. The projectors were highly regarded and came with a sound system. The amplifiers used an ECC35 or 6SL7GT as a phase splitter. This exhibit still has part of a cap M in white paint on the glass. The font identifies this as the start of the name Mullard.
The ECC35 is described by Mullard in 1957 as a high gain double triode with separate cathodes for use in para-phase AF voltage amplifiers.
The twin triode sections with fins on the tops of the copper grid supports.
The working centre of the anode is pressed into an oval shape.
The wide glass tube envelope is 30 mm in diameter, and excluding the IO base pins, is 67 mm tall.
References: Data-sheet, 1040, 1043 & 3002. Type ECC35 was first introduced in 1942.