The map describes this region as having been visited by Europeans in the 11th century. Although it was presented to the world in 1965 with an accompanying scholarly book written by British Museum and Yale University librarians, historians of geography and medieval document specialists began to suspect that it might be a fake as soon as photographs of it became available, and chemical analyses have identified one of the major ink ingredients as a 20th-century artificial pigment. Individual pieces of evidence continue to be challenged, . In 2018 and 2019, specialists at Yale University, where it is held, declared that the latest scientific and historical research has established that it is a modern forgery.