Boss SD-1 SUPER Overdrive 1986 s/n 624800 Japan in very good condition. Thoroughly tested and in perfect working order.

The SD-1 has been around for a very long time and has gone almost unchanged from its conception back in 1981. The pedal contains an asymmetric overdrive circuit that responds very well to the player's picking force. It produces a dynamic and smooth overdrive effect well suited to any type of rock music. The SD-1 is also popular as a booster pedal for valve amplifiers. Turn the distortion down and the level up and connect it in front of the amplifier. The higher input level will push the input valve of the amplifier harder producing more distortion from the amp itself. The SD-1 is well suited to do this because it maintains the natural tone from the guitar.

The OD-1 didn't have a tone control so the engineers felt that the tonal range was limited because of this. As an answer to the problem they came up with the SD-1. Comparing the two circuits reveals that they are very closely related and using the exact same overdrive circuit. When comparing the sound of the two pedals side by side, it is however obvious that they're not identical. Opinions are divided when it comes to the question, which one sounds best, but there is no doubt that they're both legendary overdrive pedals.

( Article from PedalArea )
Boss SD-1 JAPAN versus Boss SD-1 TAIWAN  
" Many times you hear rumours about how the older Japanese versions of the effects pedals are superior in sound compared to their newer, Taiwanese counterpart. In my comparison I also opened the boxes the compare the circuit boards and components with each other to see if there are any differences which might explain differences in sound - if there are any. So here's my conclusions:
On the outside the pedals are almost identical. The differences between the Japan and Taiwan versions are practically only on the label on the bottom. A peek inside the pedal reveals that the electronics and the circuit boards are very similar, but not identical. The used operational amplifier JRC4558DD ( JRC Japan Radio Company ) is the same in both pedals, and is actually quite similar (only slightly larger gain) to the op amp used in the famous and sought after TS-808 Tube Screamers.
A closer inspection nevertheless reveals some differences. The circuit boards are made of different material, the older one being dark brown, whereas the never ones are significantly lighter. Many capacitors are completely different and from different manufacturers, some of the transistors are from different manufacturers and are of different type and the resistors in Japanese version are larger than in the Taiwanese version. The components used in the Japanese version seem to be high quality components and their assembly is accurate and clean, whereas in the Taiwanese version the legs of the components are bent unevenly and the soldering is less consistent, maybe due to cost savings in the mass production lines. It is impossible to tell how much these differences affect the sound of the unit, but it is obvious that there are many differences inside the pedal that could potentially make a difference also sound wise. "

SD-1 production moved from Japan to Taiwan early 1988 and was one of the first pedals produced in Roland's Taiwan factory.
The pedal was modified for the PSA power adapter early 1997 which can be identified by the change from black to silver bottom labels.
The earliest SD-1s was shipped with the silver coloured thumb screw but this was changed to the current black screw only months into production.
A special Zakk Wylde painted SD-1 was made for Ishibashi Music in Japan 2001. These are rare and unconfirmed rumours has it that only 5 of these were made.
Specifications

Controls: Level, Tone, Drive
Connectors: Input, Output, AC Adaptor
Current Draw: 4 mA (DC 9V) (Advertisement says 4mA, the manual says 6 mA, measurements confirmed current draw to be 3.7 mA)
Weight: 400g / 15 oz (including battery)
Nominal Input Level: -20dBu
Input Impedance: 470kOhm/1 MOhm (Earlier Pocket Dictionary's says 470k, later manuals says 1 MOhm)
Nominal Output Level: -20dBu
Output Impedance: 1kOhm
Residual Noise Level: -110dBm (IHF-A Weighted, Typ.)
Recommended Load Impedance: 10kOhm or greater
Recommended AC Adaptor: ACA series (black label) or PSA series (silver label)
Labels

Black - Made In Japan
Black - Made In Taiwan
Silver - Made In Taiwan
The SD-1 was sold from February 1981 to present.