A disk-type astrolabe dated between 1496 and 1501, now the world's oldest, was discovered in 2014 by the marine scientist David L. Mearns on the wreck site of a Portuguese nau "Esmeralda," which sank off the coast of Oman in 1503. The astrolabe was confirmed by laser scanning, which revealed a series of 18 gradations marking 5-degree intervals, and has been named the Sodré astrolabe. It has been proposed that the Sodré astrolabe is a transitional instrument between the classic planispheric astrolabe from which the first mariner's astrolabes made of brass were adapted and the open‐wheel type astrolabe that came into use sometime before 1517.