Picked up a Racal 9083N two-tone generator (0 - 20 kHz) for $30 USD. These things presumably were used to test a device's intermodulation distortion. Preliminary testing shows that it works fine and both oscillators have distortion less than -80 dBc (at 1 kHz).
The build quality, as shown in the pictures, is outstanding. It's hard to see, but most of the electrolytic caps have foam cushioning underneath. The op-amps have plastic cradles, the wiring is neatly tied and routed, the front panel potentiometers big and beefy. I have several other Racal pieces, and the manufacturing quality is nowhere near this one.
But perhaps that is because Racal actually didn't make this piece??? You will note that the board is marked "KDP Electronic Systems." Maybe one of the British eevBlog members can share some light on Racal and second sourcing products.
Also, there are about 16 adjustment pots in this unit. How can I resist turning some? If anybody has either the service manual or the adjustment procedures, please send me a message. Thanks.