This instrument is based on the earliest known extant mariner's astrolabe. It was discovered in 2014 as part of the archeological excavation of the wreck of two  Portuguese naus (heavy, 3-4 masted sailing vessels) the Esmeralda and the Sao Pedro, lost to a heavy wind in May 1503 off the coast of modern Oman.* The two ships were part of Vasco da Gama's fourth armada, departing Portugal for India in 1502. From the markings on the astrolabe and the date of departure for the armada, the authors of the description of this instrument date its manufacture between 1496 and 1501. This artifact is the only solid mariner's astrolabe with solid provenance and date. It is the earliest known mariner's astrolabe and the only instrument of this type decorated with national symbols.

Maker's Notes

The instrument is 175mm in diameter and 1.5–2mm thick (6.89" dia. & about 14G). In the paper describing this instrument the authors assume it is a casting due to the thickness at the decorations, however, I am assuming for my recreation that the decorations and center area were made separately from the body and later attached as seen commonly in European planispheric astrolabes made during the medieval period.

• See Mearns, David L., Warnett, Jason M. and Williams Mark A. "An Early Portuguese Mariner's Astrolabe from the Sodre Wreck-site, Al Hallaniyah, Oman. The International Journal of Nautical Archeology (2019) 00.0: 1–12.