The VT-86 is the American Government specification, commercially this is a 6K7 variable-μ pentode that was designed for RF and IF amplifiers in 'modern' superhet receivers with AGC control.
The RCA logo.
The 6K7 indicates complete equivalence with the commercial valve Type.
The thin metal envelope is 25 mm in diameter and, excluding the IO base pins, is 64 mm tall.
References: Datasheet & 1040. Type VT-86 was first introduced in 1936.