Tinstaafl, that is not entirely correct.
Under the FAA system you hold a pilot certificate - for example Commercial Pilot. You then have Category (eg Airplane, Rotorcraft) and Class (eg Single Engine Land, Multi Engine Sea) ratings on that certificate.
In your case, you have ONE Airline Transport Pilot certificate with Airplane Single Engine Land, Multi Engine Land, and Single Engine Sea ratings. You could also have a Rotorcraft Helicopter or Lighter Than Air ratings, though it is still just the one certificate.
Under the FAA, there is no such thing as a License.