This battery (2 x PP9) powered oscillator was made by the Venner Electronics Ltd, New Malden, Surrey.  This model number TSA 625/2 was first made in 1964. The earlier model 625 has a blue front panel and some have a slide switch to select sine or square wave output rather than pushbuttons. The same instrument was also marketed as the Marconi TF2103 who continued to market it until the late 1970's. The latter does not have a "push to test supply" button which in this instrument operates a small incandescent lamp but has an LED in series with a resistor connected across the supply.

 The frequency range is 10Hz to 1 MHz in 5 switched ranges with a calibration accuracy of +/- 3% of the scale reading and the output can be adjusted from 1mV to 2.5V using the voltage selector 1mV, 10 mV, 100mV, 1V and a 0 - 2.5 potentiometer. The instrument employs eight transistors three of which together with a thermistor form a Wien bridge oscillator and two form part of a Schmitt trigger circuit which is used to produce a square wave. An optional power supply was made to take the place of the batteries if required.

 This nice little oscillator together with instruction manuals was given to me in 2014  by Richard Harvey  who remembered using one back in the days when he was a lab technician in the 1970's. He had replace two electrolytic capacitors and put in standard silicon pnp BC178 ‘s to replace the original germanium devices (which were blown). It's working and gives a nice sine wave over it's stated range of frequencies, 10 Hz to 1 MHz, using the very smooth feeling adjustment dial. The oscilloscope trace shown below is from the instrument at 50kHz.

.Dimensions.
The case measures 212(w) x 127(h) x 120(d)  mm, (not including the handle, controls, and feet).
Weight without batteries is 1.1kg.

Two views of the interior, note the modern much smaller replacement electrolytic capacitors

Venner which was founded in 1906 is more commonly known for the manufacture of time switches for street lighting columns and central heating control, they branched out into the manufacture electronic controls and measurement in the 1960's. It seems that Venner Electronics ceased and became Malden Electronics, a UK company founded in 1976 which continues to manufacture electronic measuring, testing etc. equipment