Dialect Card
Students caught using the local dialect had to hang a ‘‘dialect card’’ (a tag made of wood or paper) around their necks. They could pass the card on to another student if they caught them using the local dialect.
See also: http://en.wikipedia.org/wiki/Dialect_card
Photograph: a dialect card at Kihoin Shushukan Museum, Taketomi Island (height: 17 cm, base: 5 cm, thickness: 9 mm). From: ITANI, Yasuhiko. 2006. Okinawa no Hogen Fuda (The Dialect Card in Okinawa). Naha: Borderink.