The always amusing, always engaging Modern Mechanix blog tells about some interesting personal appearance information from the 1920s:
Many women in England, who have been divorced from their husbands, continue to wear the wedding ring, but have a fracture cut in it by a jeweler, as an indication of that fact. Those who have parted from more than one husband have notches to indicate the number made in the edge of the gold band, it is said.
Go to the post to take a look at the fractured ring (indicating the broken marriage. I do not remember reading about these notched rings in any novel; would be interesting to see if somebody at some point wrote “She wore a broken ring” or, “She wore a broken ring with n notches”.