The 1626 was designed as an RF power oscillator for conditions where good frequency stability is important. The operating condition was class C and that explains the high negative grid bias. The valve was only designed to provide short pulses of power in the anode tuned circuit. The circuit itself would then ring and generate sine wave outputs.
The base has the US service designation of VT-137 showing direct equivalence.
The anode: the glass shape generates the reflections but the copper grid supports can clearly be seen as can the grid winding above the lower mica.
The classic envelope is 38 mm in diameter, and excluding the IO base pins, is 89 mm tall.
Reference: Datasheet. Type 1626 was first introduced in 1941.