That's interesting. Fish, it's really just how they see their market running for their plastic, if you ask me. Wrap it around the coin, what's it worth? That's the "grade."
All posts considered, it's a nice Walker, but I would NOT pay a MS66 price for it. And it's a common date so you can look for a better one.
I'm not big on toning, but the toning around the rim looks fine to me, and I believe the grade is okay, as well.
Hard to completely judge the luster from the pictures. My impression is that it's still very nice. I think there is a bit too much chatter on the left leg/skirt for me. I think 65, no problem. Did you make the purchase? If yes, when do you get the coin? Can you update this thread with your impression of the coin after it arrives?