 To the north-east of the castle are the remains of a stone-walled fort.The "Ordnance Gazetteer of Scotland", published in 1892, lists a Castle Rachal in the same general location as Castle Coeffin.It is described as "a very ancient Scandinavian fortalice in Lismore and Appin parish, Argyllshire, on the NW side of Lismore island, from the north-eastern extremity, now a dilapidated ivy-clad ruin."