An American construction--the propeller mark also looks the same as the three blades of an electric fan--thus the term "fan mark." It's just a description of what the mark looks like, but whatever the term used, it is a part of the Harrach coat of arms. The U followed by the four numbers is a Harrach designation according to Brian Severn's Harrach project. Brian told me he had seen Moroccan decors in the Harrach design books and had me send me pictures of all my examples as part of the effort to unravel the design numbers. However, most of the examples of this decor that I have seen do not have any markings on the base, and do not have the cross or flower inside a center diamond that seem to be found consistently on the Harrach pieces. At least so far...I am tracking all the examples I can find in my own little "Moroccan decor" project. Manley references a Webb sketch book of 1879 but I have no idea whether the sketch really shows the same decor, which is described as alabaster-cored, with square top and enameled. My quest is to find some square-topped examples and see if they differ in some respect--markings, thickness, design, or whatever. It would be enormously helpful if one of you folks in the UK was able to take a look at the Webb sketch book of 1879 that Manley references. Thanks much, Cathy