Describe symbolism in The Loneliness of the Long-distance Runner by Alan Sillitoe

The Fishing-Boat Picture from the story by the same name is the last of three paintings that have survived from Harry and Kathy's violent fights. They call it "the last of the fleet" and it comes to symbolize better times in their marriage. After Kathy returns to Harry, she sells the picture to a local pawnshop for booze money, but is later found to have stolen (or bought) it back.