A mariner’s astrolabe with a cast brass frame which is missing the alidade and suspension ring. The mater has been made from a single casting with a bottom ballast, and has a pronounced wedge shape. This is to assist the instrument to hang the plumb in the vertical plane during an observation. Originally this was an ornate casting, much more so than is usual for a mariner’s astrolabe. The object has been badly eroded with the scale and other marks are obliterated.

Found on the seabed near Great Mewstone Rocks in Wembury Bay, Devon, by Mr Wilfred T. Jenkins of the Plymouth Sound branch of the British Sub-Aqua Club, on 29 September 1970. Lent by Mr W. T. Jenkins, Plymouth, Devon in 1971; purchased from him in 1998.

Taking into account the location of the find, this instrument may well has been English, but a more recent discovery of two similarly styled astrolabes off the Iberian coast have deepened the uncertainty surrounding this item’s origin.