John Purnell wrote to Sloane in letter 4229 to discuss a mutual acquaintance of whose name he cannot recall and medals, with some curious specimens, that he had recently sold.
One record of a merchant by the name of John Purnell is available, so it is possible that this is him, but aside from this no precise records can be found.
Reference:
John Purnell to Hans Sloane, 1734-11-25, Sloane MS 4053, f. 323, British Library, London.
Articles of Agreement, Records, The National Archive, [http://discovery.nationalarchives.gov.uk/details/r/7a21cff6-bb42-47b6-aaba-da75d75438e9, accessed 18/08/17]
Dates: to
Occupation: Unknown
Relationship to Sloane: Virtual International Authority File: