I have a model of the Imara, and on page 99 of Traplets Steam Boat Book a modeler Phil Pace converted her to the Perserverance and said she was a TID. Is this a desigination of TUG INLAND DEFENCE or a build type desigination. I am in the USA but I have used U.K. for all my reference since I started building. I feel the U.K. has the most interesting models and the best build information, and all my boats are built in, what I call the Brit fashion.. Thank you very much.