This exhibit is a generic 807 transmitting variant of the 6L6G design. It is interesting because the original 807, from all makes, was between 121 and 126 mm tall, and this version is only 116 mm tall and looks more compact. The height reduction seems to be in the length of the pinch and above pinch supports - all adding to a potential reduction in lead inductance and thus better HF response.
The parameters given are for single ended use. When used in a class AB1 as a push pull pair with 600 Volts on the anode an output power of 65 Watts was normal.
The anode, ceramic insulators and the distinctive oval screen below the lower mica.
The classic envelope is 50 mm in diameter, and excluding the UX5 base pins is 116 mm tall.
References: Data-sheet & 1040. Type 807 was first introduced in 1938. See also 1938 adverts.