The 17GT5 is a beam tetrode designed for service as a line output valve in television receivers. Designed in America the design is based on a 525 line image with a 30 Hz frame rate.
The 6GT5 differs only in having a 6.3 Volt 1.2 Amp heater for parallel connection, whereas, the 17GT5 and 17GT5A are designed for series heater chains.
The Type designation is etched into the side of the glass.
The anode is stitched together with the side flanges centred on the main electron flow. The image shows the grids end on.
The top mica with heat sink attached to the control grid supports. The cathode can be seen as a wide flat box.
The B9D base and lower mica components.
The wide glass tube envelope is 38 mm in diameter, and excluding the base pins is 74 mm tall.
Reference: Data-sheet. Type 17GT5 was first introduced in 1963. See also1963 adverts.