JVC ECA 102 Reverb unit, "Radar Screen reverberation amplifier".

This is typical of early Japanese electronics manufacturing, the overall construction is excellent, right down to the solid wood case.  The electronics are well built, they even installed a galvanized steel EMF shield under the chassis.

This JVC ECA 102 is a 1970s example of stereo reverberation units sold as consumer add-ons to their stereo systems. (The  Pioneer SR-202 was a similar stand alone reverb.) All of these units sported a display that changed along with the Reverb setting, by mechanically moving some backlit plastic diffusers.  A nod to 1970s Psychedelia.

  
There is a metal case at the bottom of the unit that looks like it could be a spring reverb unit, but other sellers have said that this is a fully Electronic reverb unit, with no springs.  The effects are pretty good, and this would be a fun addition to a studio looking for warmer retro reverb effect.  Other reviewers have said that the effect is very close to spring reverbs.
The reverb level slider lets you vary the reverb delay length from 0 to 3 seconds. The overall sound is warm, especially for an early transistor based unit.

Here's the JVC Ad copy for the ECA-102:

Description

Right in your own home, you can now enjoy the richer depth and realism achieved in professional sound studios, thanks to the all new JVC ECA-102 Radar Screen reverberation amplifier.

Simply hook it up to the tape recording and playback terminals of your amplifier or receiver, and everything you hear takes on an enriched vibrance and realism - radio broadcasts, discs, tapes, even your own voice.

A double pickup type unit with a reverberation time significantly better than any similar product now available, the compact, solid state ECA-102 is crammed with advanced circuitry, to achieve such outstanding performance characteristics as a S/N ratio of 70dB while restricting distortion to a miniscule 0.2% or less.