Simple is the best design
That's the front panel of the Zerotronics CoolSprings mono-in/stereo-out reverb unit, and it's on our list of "things to buy" here at Leisure Cove.
I love the commitment of the machine-- no knobs! Just patch in and out for a sound, and forget about controlling it! Come to think of it, that's like the inverse of a Funk Logic product.