The CV1127 is a television line output pentode. The former name was the VT127 and it was based on the Mazda Pen46.
The Raytheon logo and type designation is etched into the envelope as is the UK military stores code of 10E/231 - so clearly made for the UK.
This sticker shows a later re-testing and that it was placed back in the stores.
For high voltages ceramic insulators were used as well as the mica sheets to hold the electrodes tightly in the envelope. The control grid has a heat radiating cylinder attached to the copper support rods.
The classic envelope is 51 mm in diameter, and excluding the MO base pins is 114 mm tall.