This exhibit, an R2 rectifier, by Micromesh dates from 1933. The unusual feature is the V orientation of the anodes.
Both anodes have small cylindrical cavities containing the cathode and considerable extra wing area for cooling.
Another example of this rectifier. The base pins are spiral cut.
The anodes seen in side view are mounted to achieve the longest length within the bulb.
The active tubes are near the centre with the rest of the anode each side being used for mounting and heat sinking.
The base of the rectifier pair. This shows the filaments are wired in parallel.
The Filaments are in fact insulated. The cathode tubes are connected together at the top and then to a strut that passes behind the anodes and fixes into the pinch. Part way down the strut a tape is taken to the right hand filament connection. This tape can just be seen in the image.
The balloon envelope is 57 mm in diameter, and excluding the B4 base pins is 102 mm tall.
References: Datasheet & 1043. Type R2 was first introduced in 1933.