The N329 was designed for low frequency power output either as a television frame output valve or for audio use.
This valve would normally be found in the single ended audio stages of television receivers, but a pair used in push pull class AB1 would deliver 9 Watts at 4 % distortion. The peak to peak grid signal voltage would be 26 Volts and the shared anode load would be 4,000 Ohms.
The Osram label.
The ceramic insulated heater passes through the cathode 14 times in seven hairpin loops.
The thin glass tube envelope is 21 mm in diameter and, excluding the B9A base pins, is 69 mm tall.