The Maestro Phaser is an phaser effect from the 70s with an very interesting enclosure design. knobs are on the side of the pedals, and have numbers on it, indicating the value.
Manual of the original:
The Phaser has 2 controls: "Balls" (which is basically Depth) and "Speed" (Rate of the phasing effect)the more the Speed turned up, the more vibrato / tremolo wise it sounds. Thick phase sound on the slow settings
The original was a 5 stage phaser using the CA3094 chip. Also the enclosure was very huge.
An excellent project which is similar to the Maestro is the madbean Stage Fright.Its actually an improved version, which an additional switch, which allows you to select between 5 and 6 stages
Can be found in the Stage Fright build dochttp://www.madbeanpedals.com/projects/StageFright/StageFright.pdf