A cornfactor is a dealer in corn or grain; a corn-merchant. John Paynter and his nephew, John Wynne Paynter, were cornfactors in the port of Amlwch, Anglesey in the 19th century.
It appears that the Paynter family came originally from Cornwall. John Paynter, in the 1841 census, is described as a corn and timber merchant, living at Maesllwyn, a substantial house. He died in 1843 and left his house to his nephew, John Wynne Paynter and he also became a prominent merchant and magistrate.
For a thorough understanding of the industrial and maritime importance of Amlwch in the first half of the 19th century consult Copper Mountain by John Rowlands, 1966.