What does 925 followed by a cursive D on a ring mean?

The markings "925" and a cursive "D" on a ring indicate that the piece is made of sterling silver, which contains 92.5% pure silver and 7.5% other metals, usually copper. The cursive "D" likely represents the manufacturer's or designer's initials or logo. This combination suggests that the ring is both of quality material and has a specific brand or designer associated with it.