That is a rather nice screw barrel pistol. I suspect it is a late gun due to the double neck cock. But those guns were made in the late 18th and early 19th century - they would have been obsolete by the 1880s so it is not easy to see a connection between the pistol and a ship that sank in 1882. Perhaps the supposed connection with a whaler misled someone, but that stock looks like ivory to me.
There were a number of ships named Sappho, including four ships of the Royal Navy, one of which was an 18-gun brig-sloop launched in 1806, a much more likely date for that pistol and in line with the time Bond was active.
BTW, those are often called "Queen Anne" pistols, but Queen Anne died in 1714, long before the screw barrel became popular. Does anyone know what the connection was or why the guns came to be called that?