The Amplion AML2/30 is a rebadged Cosmos SP-18RR and was introduced in the 1926-28 period as an output valve. It announces that it is a shortpath design on the valve lettering.
The amplification factor or μ is 6.5.
The small electrode assembly is mounted vertically on the pinch.
The flattened shape of the anode and the oxide coated single strand filament.
The top of the electrodes with the filament top support in the foreground.
The helical control grid is secured to the side support with thin wire wrapped over each loop.
The balloon envelope is 25 mm in diameter and, excluding the B4 base pins, is 99 mm tall.
References: Data & 1043. Type AML2/30 was first introduced in 1926. See also1926 adverts.