Note: Do not rely on this information. It is very old.
Cup Markings
Cup Markings, a collective name for cup-like depressions on prehistoric sepulchral monuments and on stone weapons and implements. In the former case they are of two kinds - simple cups, and cups surrounded by concentric circles, and nothing is known of their origin or purpose. In the latter they seem to have served to afford a firm grip, and in some instances show that the stone was used as a journal or bearing.