scarlet letter
n.— «Two senators unveiled a measure Thursday that would require drivers convicted of three drunken-driving offenses in a five-year period, or four within 10 years, to purchase license plates with a number code that police could use to identify them as convicted drunken drivers.…In Ohio, the plates are known as “scarlet letters.”» —“DWI plates would ID offenders” by Amanda Erickson in Albany, N.Y. Press & Sun-Bulletin (Binghamton, N.Y. ) June 17, 2005. (source: Double-Tongued Dictionary)