When Kurogane's watch loses its paint, I suggest you renovate it by coating it. For example, buy a bottle of black paint for watches, then dip it carefully with a cotton swab, apply it to the place where the paint has fallen off, and then wait for it to dry. Conditional people can also choose the way of coating to maintain watches.
Paint peeling is a normal phenomenon, especially for people with high exercise intensity. Once the watch is not well protected, it is also common to lose paint.