Mourning rings were usually paid for by the person commemorated, or their heirs, and often specified in wills. Sometimes the metal required was melted down from the persons belonging or scrap jewelry and made quickly by local jewelers for the relatives to wear during the mourning period. As Catherine & Henry had no children, it's possible this ring was made for Henry's sister, Janet who was married to William Bruce of Newton.
Gold is unmarked but tested positive for gold over 14k. Weight 7.75 grams, excellent overall condition, minor scratches on glass cover over sepia, visible with jeweler's loupe.