"Proto" series The series is named Proto, which means "early" or "prototype". With a simple design, it is a basic and minimalist series that does not dare to add design. The slightly larger hoop earrings created by the original are items that can be used both in mode and casually with the simplicity of the material. K18 is coated on top of SILVER925 (sterling silver) and the high quality of metal is added, so you can use it as a higher-grade gold color.