The Boss DM-2 analog delay pedal was sold from 1981 to 1984 and is still sought after thanks to its warm, natural sound. Produces a delay time ranging from 20 to 300 milliseconds, and has 3 knobs (Repeat Rate, Intensity and Echo).
Fig. 1: Boss DM-2 Delay guitar pedal schematic diagram
Fig. 2: Boss DM-2 Delay circuit board - component and foil side
According to this page on BossArea.com, there are at least 3 different versions of this circuit. The first DM-2 version was using the MN3005 BBD and the MN3101 Clock Driver IC (PCB marking: ET5214-510).
Later they changed the clock driver to MN3102 and the BBD to the low current version of the same circuit, the MN3205 (PCB markings: ET5214-510A and ET5214-510B). The MN3205 is a little noisier, but it generates less distortion (only 0.8% compared to 1% for the MN3005).