demo to showcase both the Rolling REC-4 unit and the Elka Solist (and not Soloist) 505.
The Rolling REC-4 is rebadged Evans Echopet EP-250, exact same PCB (labeled EP-250 by the way). It's a very nice spring reverb and BBD delay combo. It uses 3x Panasonic MN3005 chipsets, the same used on more famous BBD delay like the Yamaha E1005 / E1010 and Ibanez AD202 among many others.
What's make it quite unique is that the delay sound goes to the reverb tank so you can get some very dense effect. If you want only the spring reverb sound you need to leave the "repeat" control of the delay fully counter clockwise.
The Elka Solist 505 is a simple italian monophonic analog synth with preset and some limited sound editing control, like a simple attack release enveloppe that can be routed to VCF or VCA, a "wow" effect, which is more or less a resonance control; cutoff control, vibrato depth (speed is fixed) and "bend".
It is however very nice sounding because of the Moog inspired transistor ladder filter.