The 6BQ7A is an all glass miniature VHF double triode and is internally screened.
The 6BQ7A would be used for cascode RF amplification, or possibly frequency multiplication. In the latter case the valve is operated as a non-linear (Class C) amplifier. This causes harmonics of the signal frequency to appear in the anode current. The anode tuned circuit is then chosen to resonate at one of the harmonics, usually the second or third.
The RCA Logo and triode anode face view.
The twin triodes seen end on with the electrostatic screen between them.
The thin glass tube envelope is 21 mm in diameter and excluding the B9A base pins the valve is 47 mm long.
References: Data-sheet & 1040. Type 6BQ7A was first introduced in 1954.