This exhibit is probably an audio output valve but it has no markings. The construction features a clip that has been tightened round the stem of the pinch and its function is to support the anode. This suggests a professional set of applications.
The anode is a box structure with indentations to add extra rigidity.
The filament seems to be 6.3 Volts and takes 1.1 Amps. The construction is oxide coated ribbon.
The classic envelope is 47 mm in diameter, and excluding the UX4 base pins is 135 mm tall.
Updated June 20, 2013. shape:classic construction:pinch type:triode base:ux4 heater:6.3v pins:4 pin: