The TD03-10 is an indirectly heated disc seal triode, without internal feedback, primarily intended for use as a common grid, earthed anode, concentric line oscillator. It has a 10 Watt anode dissipation and can also be used as a power amplifier.
The anode ring is on the left and inside the glass the flat ended copper cone is the anode. The flat end is placed very close the fine wires of the grid. The grid is in effect a frame grid where the frame is the supporting disc. The cathode is also flat ended and placed close to the other side of the control grid.
The thin glass tube envelope is 16 mm in diameter, and including the base pin is 61 mm tall.
References: Data-sheet & 1040. Type TD03-10 was first introduced in 1945. See also 1945 adverts.