Alexander McCall Smith, Corduroy Mansions
(2009; rpt. New York: Anchor Books, 2011), pp. 80-81:
This technique of asking just the right question to inhibit further conversation was a useful one, and was used by William in other social circumstances when small talk needed to be avoided. At cocktail parties, where one might quite reasonably simply wish to stand, or sit, and not be pestered by other guests seeking to make small talk, the use of a discreet lapel badge was sometimes to be recommended. This badge might state one's religious position in unequivocal terms, and invite discussion on it. Thus a small badge saying "Please talk to me about Salvation" usually had the effect of ensuring a peaceful time at any party, leaving one untroubled by other guests coming up to engage one in unwanted conversation. Similarly a badge saying "No longer infectious" could usually be calculated to ensure physical space, another commodity in short supply at the more popular cocktail parties.
Hat tip: Mrs. Laudator.