A stunning original manuscript copy of a portolan atlas by Grazioso Benincasa is valued at £1.5m-2.5m ($2.4m-4m) ahead of a sale at Christie's London.
The lot is to headline the Valuable Manuscripts and Printed Books auction on November 19.
Portolan charts are made at sea, using compass readings to build up a picture of the coastline.
The present example is the first known map to show the coast of West Africa and includes depictions of the Cape Verde Islands.
Benincasa was a 15th century Italian mapmaker who travelled with Alvise da Cadomosto and Pero da Sintra - the sailors hired by the king of Portugal to map a route to Africa in 1455 and 1456.
Of additional importance is the inclusion of the earliest individual map of Ireland. All of the charts are held in their original "backless" binding.
A huge archive of personal correspondence from Italian opera singer Enrico Caruso (1873-1921) carries an estimate of £150,000-250,000 ($240,473-400,788).
Caruso was one of the most famous tenors of the 20th century, performing at some of the world's most prestigious opera houses over the course of his distinguished career.
The huge number of letters and telegrams span the course of his life. Some were sent to close members of family, while others are heartfelt letters to Ada Giachetti - the great love of his life.
Earlier this year a Roman gold aureus formerly belonging to Caruso sold for $117,000 at Baldwin in New York.
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