The CV1722 is a tetrode. The prototype was the A901. The old GPO code is POVT179.
The GEC brand sticker on this M-OV valve.
The inner coating makes seeing the structure difficult. In this enhanced image the basics are clear. The cathode tube is a rectangle with at least four heater strands within. The control grid is wound on copper supports.
The classic envelope is 44 mm in diameter and, excluding the B7 base pins, is 99 mm tall.
