This valve has no identification other than a paper label. The Type 2151 is a pentode, as the image confirms, but no further details have been found.
The blackened anode has an oval cross section and there is a heat sink on the control grid supports. The control grid has been wound on copper rods and the third grid is of wire - a true pentode.
The pressed anode has been stitched together. The control grid heat sink is in the shape of a U.
A closer view of the top mica and grid supports.
The classic envelope is 44 mm in diameter, and excluding the UX6 base pins is 100 mm tall.
Updated June 25, 2018. shape:classic construction:pinch type:pentode base:ux6 pins:6 pin: