The KTW63 is a beam or kink-less tetrode for HF and IF amplification in broadcast receivers and replaced the W63. The valve is variable mu designed to have the stage gain controlled by a voltage derived from the final rectified signal.
The paper Osram Label.
The typical M-OV style of identification. Sadly little detail can be seen of the electrode structure.
The classic envelope is 38 mm in diameter and, excluding the IO base pins the valve is 102 mm tall.
References: Datasheet & 1040. Type KTW63 was first introduced in 1938.