GtP stands for Gouda Tobacco Pipes. The pipes are made in Gouda, The Netherlands, by a man named Adriaan van der Want. He is the last in a long line of Gouda clay pipe manufacturers. The pipes are very pretty to look at and they come in different sizes, shapes and colours. I have 3 GTP pipes, never bought one though. The pipes give a reasonably cool smoke especially compared to the traditional long Gouda clay pipes. However they tend to get hot and because they have a double siding you can get some trouble with [moisture]. As far as clay pipes go, the GTP pipes are rather good.