Gerard De Visme was the fifth son of Philip, Count de Vismes and Marianne daughter of Piquet, Marquis of Magaens, French Hugenôts who took refuge in England where members of that family had previously resided. He came to Lisbon in 1746 at the age of twenty and remained there until 1792. His firm was known as De Visme & Purry, subsequently becoming that of De Visme & Co. as shown in the «Almanach» published in Lisbon, 1794.
The British Historical Association / Lisbon Branch
Seventh Annual Report, 1943, p. 40