Since these dueling fellows were in the Royal Marines, I assume they were either from Britain or from Canada. The time period you give is well after the Revolutionary War. Oldham is a rather common name in and around Leicestershire, England. In fact, while snooping around in their County Record Office a few years ago, I looked in the card file, and, lo and behold, there was a card on a Richard Oldham--but not one of my numerous Richard Oldhams, originally of Northern Neck Virginia, but wandering off to Orange Co. NC before the Revolution and from there, some of them to Madison Co., KY ca 1775 and later. E.W.Wallace