The 9D7 is a variable μ pentode. Brimar do not give a designated frequency range in their literature. As variable μ pentodes are used in AGC amplification systems, this suggests a role in IF amplification at up to 10.7 MHz.
The visible surface within the envelope is the screen connected to pin6.
The getter residue is at the top of the glass. The silver patch on the side is present to catch any gas evolved from the glass during operation.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 49 mm tall.
References: Data-sheet, 3002 & 1040. Type 9D7 was first introduced in 1958. See also1958 adverts.
