The SC1/1400 is a high voltage low current voltage stabiliser.
The central tube and ceramic insulators.
The anode connects to the central rod that runs the length of the tube.
The thin glass tube envelope is 18 mm in diameter, and excluding the B7G base pins is 65 mm tall.
References: 3002. Type SC1/1400 was first introduced in 1959. See also 1959 adverts.