Bill, I don't know much about grading of Canadian coins - I was raised on more European grading standards which I thought Canada followed. Using US standards I would raise the grade to VF or possibly EF. This coin is, as you note, well struck but does not have more than 20-30% luster on the best side. It was apparently stored for some time in an old Whitman style cardboard holder so that the rim and edge are heavily oxidized with the black "silver sulfur" compound. The streaks on the King's portrait are a similar compound.
I was not bothered by the price or actually the resultant cost as much as the way it was described. There is simply no way there is a "fill" in the 6. It is simply a bright area exposed by carefully scratching the surface. I am upset only that he made a point of mentioning that "fill" when it was only a scratch.
He already left me a positive feedback for the payment and is open if I choose to Whack him with a negative.