Original Date Of Manufacture:
The Super Overdrive is a BOSS classic. It provides a very warm, natural sounding crunch without much extra noise. This is most certainly an analog pedal, with the JRC4558D op-amp providing the classic tone. It's often said that newer Taiwan-made versions of the SD-1 don't provide the same warmness as the older versions, from Japan. This pedal provides a nice tone, good for either standalone crunch, or for a boost. As a standalone, this effect manages to get a sag effect, much like larger tube-based amplifiers. It's also a great booster, with the level turned high and the drive turned low, used to overdrive the input of your amp or other effects with a little bit of increased gain and volume. Sooner or later, the SD-1 finds its way into just about everyone's collection, once they realize the gem that this pedal is.
This pedal's circuitry closely resembles the famous TS-9 pedal from Ibanez. Many people on the net will modify this pedal to essentially become a TS-9.
Information gathered from personal experience.