So to be honest other than what appears to be "S . D" on the one side of the coin, it's hard to make much else out. There might be lettering around the rim of the other side, but it could also be my imagination. If you're willing to take some more pictures with extra lighting (like a lamp next to you or outside in the sun) and or with magnification (i.e., put a magnifying glass or a loupe in front of the lens of the camera) that would probably help -- almost looks dirty still too. Up to you of course.
In the mean time I'm going to throw out my wild suggestion that this is a bridge toll token, because what I see looks like the Golden Gate bridge. No idea what the S D would be though.