The firm of Van Keulen was founded around 1678 by Johannes van Keulen (1654-1715) and in 1680 he published the ‘Zee Atlas’. The multi volume ‘Zee Fakkel’ followed soon after. On his 50th birthday he left the management of the firm to his talented son Gerard (1678-1726). Gerard set about replacing many of his father’s sea charts the first of which was published in 1698. This example was first published in 1734 and is a superb detailed chart of the harbour of Mahon in the island of Minorca in the Balearic Islands of Spain. The chart depicts the whole of the harbour from the St. Phillips Castle and St. Phillips Town to the town of Mahon itself. It includes roads, anchorage’s, soundings and other details. The inset lower right contains a profile view of the town and harbour. De Vries, Schilder etc. ‘The Van Keulen Cartography Amsterdam 1680-1885’, pp. 44 & 202-5; Koeman IV p. 389 no. 305; Map Forum ‘Checklist of Charts of Mahon Harbour’ no. 19.