If you live in frozen ground territory, all coins will have some micro-scratches from frost heaving, gold, silver, even copper and nickel. But the softer ones, gold and silver will suffer more. Even some that appear nearly AU can be determined dug. Think about it, that ground has been freezing, contracting and expanding for however many years the coin was in the ground.
Had a few early dimes that looked so pristine I could call them perfect. Coin shop owner told me they were dug after looking closely and seeing these microscopic scratches that were fairly invisible to the naked eye. The damage was fairly uniform as well, demonstrating a pattern that might only be described by the frost heaving process, so very minimal though it was.