Joseph describes plates as "gold plates."
Joseph Smith, History, circa June 1839–circa 1841 [Draft 2], p. 5, The Joseph Smith Papers website, accessed August 11, 2021
He said there was a book deposited written upon gold plates, giving an account of the former inhabitants of this continent and the source from whence they sprang. He also said that the fullness of the everlasting Gospel was contained in it as delivered by the Savior to the ancient inhabitants.