 Ratings and engineers often transferred freely between vessels of the three services, although masters and mates had to be rated individually on each of the three types of vessel.The Fleet Coaling Service, renamed the Fleet Fuelling Service sometime between 1914 and 1926, operated harbour and coastal vessels carrying coal and fuel oil to Royal Navy vessels.Its masters did not have to be so highly qualified as the masters of the other two services and were paid considerably lower salaries.