Picture courtesy of Erkki Hakalehto, Finland.
This unusual piece of equipment was actually a stand-alone spring-reverberation unit that also incorporated an internal 6 watt amplifier feeding a 10" x 6" eliptical speaker. The idea it seems was to use the unit in conjunction with a normal non-reverb amplifier. As well as the reverberated sound being put through the small built-in speaker, reverberation effect could also be fed into the accompanying amplifier in various degrees by means of an output balance control. A Hammond spring-reverberation was used in the Stereo Reverberator. which had two channel controled by separate volume controls and each with two inputs.
The unit was also built into a contemporary Fenton-Weill amp, the Auditorium 21, providing a hybrid though unconventional solution for the guitarist who was looking for an amp with a built-in reverb effect.