The Type 46 is an American 'dual grid' audio amplifier. The data-sheet offers a fascinating insight to the complex uses of this valve. Including service as a class B amplifier (with both grids tied together) as a class A amplifier with the outer grid connected to the anode.
Chris Cusick has a Silvertone 1654 12 valve set that dates to 1933, and is the earliest date we have for the Type 46, that uses three Type 46's in the audio stage. This is just the configuration suggested in the data-sheet. A class A driver feeding a pair operating in class B.
The filament is oxide coated ribbon. The control grid is wound on copper supports for better heat dissipation and the screen grid is clearly seen in the picture.
Seen through the top mica the coated filament loops and their support springs become visible.
Looking directly down on the top mica the grids can be seen. They are clearly shaped as the end supports are single rods and across the broad face of the anode the grid wires are straight and parallel to the anode.
The classic envelope is 51 mm in diameter, and excluding the UX5 base pins is 118 mm tall.
References: Data-sheet, 1043 & Chris Cusick. Type 46 was first introduced in 1933.