The 63SPT was A C Cossor's type designation number for the EF50s that it made and, in the case of this valve, for valves made by someone else.
This valve is marked made in USA and is painted grey which is different to our other Cossor 63SPT. In a 1951 advert for Cossor in the Radio Valve Data book printed that year the 63SPT featured appears to be of the form shown above. The only difference is that the valve in their picture says made in the UK.
The valve was so important during WWII that several manufacturers were involved although the design was a breakthrough for Philips in The Netherlands.
The wide metal tube envelope is 32 mm in diameter and, excluding the B9A base pins, is 60 mm tall.
References: Datasheet & 1043. Type 63SPT was first introduced in 1939.