One made by Troughton was issued by the Board of Longitude in 1791 to an astronomer who was joining Captain Vancouver on the north-west coast of America.
Esinye esenziwa nguTroughton sanikezelwa kumqwalaseli zinkwenkwezi owayezibandakanya kumphathi mkhosi uVancouver kumntla-ntshona Melika, isikhombisi eso sanikezelwa kuye yibhodi yezide ngo1791.