A family business founded over three decades ago, ADCO combines diamond expertise with unique artistic sensibility ADCO Diamond is one of Boston’s finest family-owned diamond businesses. Established over 32 years ago, they specialize in GIA-certified, conflict-free diamonds for engagement rings and other jewelry. Upon entering their showroom, one immediately senses the artistic and creative side of this establishment, from the unique pieces in their modern showcases to the colorful custom art work on their walls. And, combining their sense of design with the diamond expertise of the GIA-trained gemologist staff, it’s understandable why they are one of the prominent jewelers in the area.