The P225 is a battery audio pentode with an output of up to 0.5 Watt.
The bright anode has flat sides with rounded ends.
Looking at the top mica the grids can be seen as can the twin inverted V's of the oxide coated filament. In the foreground can be seen the filament tension springs.
The pinch and lower mica as well as a clear view of the etched identification.
The classic envelope is 40 mm in diameter, and excluding the B5 base pins is 95 mm tall.
References: 1043. Type P225 was first introduced in 1933. See also1933 adverts.