confused about a cleaning

1907Quarter

In my recent thread (opinion on a seated dollar) I could have sworn that the coin was so grey that it could never have been cleaned. It was pointed out to me that it was cleaned. How does one tell a cleaning if the color is dark grey?

Placid

I think it was me. I based that mainly on looking at the arm. It looked to have some dark spots in pits on the arm while the rest of the arm is bright silver in color.