I have no clue how old it is. All I know is that it's one of the old assed Japanese made Boss pedals. And I have to say... The stories of the older Japanese made Boss pedals kicking all kinds of ass over the newer Taiwan made ones is so true. I've had my share of newer SD-1s(because they are so cheap) and none of them have EVER sounded like this one. Much smoother and a bit more quiet.
I need to find a way to record some decent sounding clips with this thing.
And it's late at night right now so I can't be really loud but so far, I don't notice any loss of bottom end like I do with other overdrive pedals.
Make sure if you run it with adaptors to daisy chain it to something else - the black label models predate the Boss PSA and can fry if they aren't connected to something else first!