The E1824 is a development valve from M-OV. In this case it is a planar RF disc seal tetrode. The two grids are connected to the central rings. The top pin is one side if the heater and the small top ring is the other heater connection and the cathode. The anode connects to the large heat sink seen here at the bottom of the image.
The central metal anode is surrounded by folded metal tape and enclosed by an outer ring. Cooling is by filtered air forced through the large area of metal tape.
The central bright tube is the cathode. The copper cylinder on the right is sealed into the glass. This copper cylinder has three connections that pass into glass beads where there is a gap in the wire thus insulating the grid from the cathode. The wires then pass through holes in the grid support and are welded to it. The grid connects to the first external ring which appears to just be a push fit onto the brass grid support. The second grid is hidden but seems to be mounted on the second ring.
The planar envelope is 21 mm in diameter, and including the base is 91 mm tall.