The E1980 is an M-OV experimental valve. This carries the serial number 46.
No details could be found but close observation revealed the base connections. Through the holes in the top mica it was possible to confirm that the triode grid was connected to grid three of the main hexode section.
Here the top triode section can be seen. The grid is at 90 degrees to the hexode. The lower section shows connections to four grids with the triode grid connection on the left passing to the g3 support.
A poor image of the triode section. The bright anode is rectangular with an open front. The grid is seen end on. The cathode is common with the lower section.
The thin glass tube envelope is 18 mm in diameter, and excluding the B7G base pins is 46 mm tall.