A marriage stone is usually a stone lintel carved with the initials of a newly married couple with the date of the marriage.
The stones were placed where they would be easily and frequently seen by visitors, usually on the lintel above the front door of a house or in a prominent position facing the entrance or in the gardens, such as above a doorway in wall.
I took a walk on the beach, the second day of the present year
I saw this symbol
I took it to our home
Mother Nature is the best craftsman