Sir Francis Drake's heroic voyage around the world on the Pelican, later called the Golden Hind (December 1577 - September 1580), followed hard upon the discovery of a large bay (thought to be a strait) off the east coast of North America by Martin Frobisher in August 1576, which is also commemorated on this unusual medallic plaque. Its maker, Michael Mercator, best known for printed maps, was well informed about Drake's route, even showing - with the dotted line - the digression in the Pacific Ocean (the first time it had been sailed by an English ship) caused by a storm which lasted fifty-two days. Although these voyages were celebrated as great adventures, they were undertaken primarily to establish trade routes and to gain the riches that could be derived from the discovery of new territories. England had gone into competition with the Spanish and, starting in December 1578, Drake raided many Spanish ports on the western coast of South America, including Lima and Panama (named on the map), looting large quantities of gold and silver. It was therefore appropriate that Mercator chose to make his map from silver. It may have been the symbolic nature of the medium which caused Mercator to invent a technique for medal making that had no known precursors.Although at first sight they appear to be individually engraved, Mercator issued a group of silver maps as an edition. The few examples that survive today copy each other exactly in every detail. Mercator must therefore have developed a technique for producing multiples. Although it is sometimes assumed that they were struck using engraved dies (a technique quite close to the printing of maps), examination under a microscope shows that they were actually cast, presumably from an engraved original. This method was later used by the de Passe family for the production of silver portraits of the Stuart royal family.