"Proto" series The series is named Proto, which means "early" or "archetypal". Signet rings are said to have the oldest historical background in jewelry. Originally, a round or square pedestal with a family crest carved out was called a signet ring and was worn on the little finger of the left hand. By daring to finish it plain, it creates a sharpness that minimizes waste, and gives an elegant impression by wearing it. Originally a gentleman's jewelry, signet rings have become unisex jewelry loved by both men and women in modern times. It is a ring that goes well with any fashion and is a styling accent. K18 is coated on top of SILVER925 (sterling silver) and the high quality of metal is added, so it can be used as a higher-grade gold color.