Regarding the ring size, the inner diameter is listed. (We apologize that we are unable to provide tools to measure the ring size.) This is a retro ring. ◎ The metal fittings are silver-plated. ◎ Inner diameter: Approximately 19mm (According to my online research, it seems to be about size 19) The back seems to be slightly open, allowing for minor adjustments. It is possible to make the size smaller by overlapping the metal fittings, but the strength of the fittings is unknown. ◎ There are scratches, discoloration, and dullness.