The 6AF4A was designed for TV service as a UHF oscillator in front-end mixers. Typical frequency of operation would be 0.95 GHz.
The Pinnacle logo on the envelope. Within can be seen the copper control grid supports.
The anode is indented on both sides to place the rectangular working area as close as possible to the grid whilst keeping the majority of the anode clear so as to remove heat from the tiny active centre.
The thin glass tube envelope is 17 mm in diameter and, excluding the B7G base pins, is 38 mm tall.
References: Data-sheet & Data. Type 6AF4A was first introduced in 1954. See also1954 adverts.
