This exhibit has no identification on the envelope. The construction follows the pattern of the Heil Tube with the electron beam passing horizontally across the tube via a resonating cavity. Unlike other Heil tubes the resonator is connected to both a 41mm diameter flange and a top-cap as well as pin 6 on the B7G base.
The anode plate is on the right of the central copper resonator.
The anode is the grey plate. Pin one is missing as is pin 3.
The central resonator tube with electron source above. The second grid appears to be a thin vertical slit with no wires. The anode is at the bottom of the image.
The top-cap can be seen to connect with the resonator and flange. With care the g2 slot can be seen below the electron source.
The thin glass tube envelope is 19 mm in diameter, and excluding the base pins is 72 mm tall.
Updated July 30, 2016.