The type 41 is a high gain audio output pentode that is electrically identical to the type 6K6GT. It was designed for single ended or push-pull use in the output stages of domestic equipment.
Although clearly marked as an RCA product, the base is also marked with the Cunningham name as well. The envelope also carries the ADZAM brand.
A close-up of the bottom of the electrodes. The control grid is clearly wound on copper supports for greater heat conduction. Above the top mica sits a U shaped heat sink attached to both supports of the control grid.
The classic envelope is 38 mm in diameter, and excluding the UX6 base pins is 88 mm tall.
References: Datasheet, 1040 & 1043. Type 41 was first introduced in 1936.