This is the oldest HP instrument that I own.  It was the first major success for HP - Disney studios purchased several and used them to create electronic sound effects for Fantasia.  It covers 20 Hz to 20 kHz in three ranges and uses the same lamp-stabilized RC circuit that was the foundation of the HP audio oscillators for decades.  The illustration is from the July, 1946 issue of Communications magazine.

This is the beast of the HP 200 series of oscillators - maximum output is 3 W (42.5 V) into a 600 Ω load.  Frequency coverage is 20 Hz to 20 kHz in three ranges.  Maximum distortion is 1% at maximum output.  I use this oscillator as the signal source for a number of General Radio audio-frequency bridges.

Here is a classic solid-state instrument.  The 334A is much easier to use than my GR tubed distortion analyzer (and much smaller).  This was the top end of the four original solid state HP DAs.  The distortion measurement range is 0.3% to 100% full scale, 0.1% is the smallest accurate measurement, and the fundamental frequency range is 5 Hz to 600 kHz.  Voltmeter range is 300 μV to 300 V full scale, 100 μV is the smallest accurate measurement, and frequency response is 5 Hz to 3 MHz.  The instrument has auto-nulling and an AM detector for measurements on AM radio transmitters.

This instrument provides 1 to 110 dB of attenuation in 1 dB steps for measurements in 600 Ω audio systems.  Frequency response is DC to 100 kHz.

This tubed general-purpose sine wave oscillator covers 10 Hz to 10 MHz in six bands.  Maximum output is 3 V into 600 Ω (15 mW).  Maximum distortion is specified at less than 1% below 100 kHz, increasing to about 5% at 10 MHz.  This instrument has a step attenuator covering 50 dB in 10 dB steps and an output meter, and because of its accuracy and stability it should be called a generator, rather than an oscillator.

This solid-state successor to the 650A covers 10 Hz to 10 MHz in six bands.  Maximum output is 3.16 V into either 50 Ω (200 mW) or 600 Ω (16 mW).  Maximum distortion is specified at less than 1% below 5 MHz, but mine measures 0.12%.  This instrument has a step attenuator covering 90 dB in 10 dB steps and an output meter, and because of its accuracy and stability it should be called a generator, rather than an oscillator.