Ever Ready are known as makers of dry batteries and at one time they made some valves. Later a deal with Mullard allowed Ever Ready to sell their own brand of valves that were made by Mullard. The K30G is in fact a Mullard PM2A.
This audio valve could drive a small loudspeaker it had an output rating of 0.15 Watt at 5% distortion.
The brand identification and Type designation are etched into the top of the glass.
The electrode assembly is mounted horizontally and the oxide coating on the filament looks to have been formed by the Azide process as the inside of the glass is blackened.
The balloon envelope is 46 mm in diameter and, excluding the B4 base pins, is 92 mm tall.
References: 1931 data-sheet & 1043. Type K30G was first introduced in 1935. See also1935 adverts.