These large brooches are used to attach the plaidie (tartan shawl) to the shoulder when in Highland dress. Note the longer pin which in Victorian times was necessary as the fabric was thick - especially tartan made of wool. It has a "C" clasp and the surround is either brass or a gold fill with not too much wear. The agates are great in color and in good condition for this brooch of around 150 years old. It measures 2 3/4 inches across and the center was often used for either pictures or hair. The backing is slate.