The grade is VF details, environmental damage. It appears to have been in the dirt, and has rough surfaces. The value is probably around $60-$75. Yours appears to match the O-101, which is one of the most common marriages for the year.
I agree with environmental damage. Although I would say it was recovered not from dirt, but from the water, possibly a lake or river. Bodies of water usually turns silver black like that. I've seen and it happens a lot, silver coins recovered from the ground that look like they were just lost.
