The color and pattern is that of a coin recovering too quickly from a chemical stripping. The obverse, though, presents the appearance of a mechanical cleaning with all the dark stuff in the tight areas. A brushing that hard would leave plain signs, though. I'm of the opinion it's been dipped within an inch of its' life, and it was so thick in those areas that the process was abandoned before it ate the coin away. The obverse must have been dark. Don't think it's beyond help, though.