Copy of the so-called "Valentia astrolabe"

(named after its site of recovery on the Irish coast; Greenwich, National Maritime Museum: A.55/54-13; see http://www.nmm.ac.uk/collections/displayRepro.cfm?reproID=F5272-001#content),

For further information see

http://www.dehilster.info/instrumenten/astrolabe/index.html