Coal Hill School tie

The official Coal Hill School tie was black with thin, diagonal, green stripes. The First Doctor once used Ian Chesterton's Coal Hill School tie to test whether a liquid discovered on the planet Vortis was acidic. The test was positive, so the tie disintegrated. Ian was perturbed at the loss of the familiar object, until he understood that the test had saved his life. (TV: The Web Planet)

Years later — at the dawn of the 21st century according to one account — an older Chesterton encountered a stranger while walking in London. They had a brief and enigmatic discussion about the nature of time, and then Chesterton continued on his way. When he arrived at home, his wife Barbara said that a strange man had left him a package. When Chesterton opened the package, he discovered a brand new Coal Hill School tie. (PROSE: Untitled)

By the 21st century, the Coal Hill School tie was only worn by students, and the colours changed to equally thick white and black stripes. (TV: The Caretaker (TV story))