The 6BW4  (P/N 154-0119-00) is a dual diode vacuum tube where both diodes share a common cathode. It has a 6.3 V heater and a B9A (Noval) miniature 9-pin base.

The 12BW4 is identical but with a 12.6 V heater.

Used in

Some instruments using part 6BW4

Instrument Manufacturer Class Model Description Introduced
126 Tektronix Plug-in 126 Power Supply Module 1952
502 Tektronix Oscilloscope 502 1 MHz dual beam differential scope 1958
502A Tektronix Oscilloscope 502A 1 MHz dual beam differential scope 1963
524 Tektronix Oscilloscope 524AD TV waveform monitoring scope 1953
575 Tektronix Curve Tracer 575 Curve tracer for transistors 1957