Joseph Askwas is a highly uncommon name. However, ascuas (ember) is a common word in Spanish and José Ascuas is a common name in South America. Guano is a product from a.o. South America, in particular Argentina and Chile. The most obvious flat island is therefore the one in the Falklands, near Argentina, which would explain the South American family name, its Anglification, the use of English on the medal and the guano - the Falklands was a way station for guano destined for Britain.
Peter