Official handbook published for military use with the probable end of WWII in mind. Although it was produced by a department within the Admiralty, I don't think the Royal Navy really thought that they would ever find themselves calling at a Luxemburg port: it was probably just that all the production of such handbooks was concentrated in one department and the Admiralty had the necessary skills. My copy is marked "Restricted", but a label from a civilian library has been stuck over where it used to say "for the use of HM forces only".
Lots of background information on the physical geography, economy, resources, infrastructure and political system of the country of the sort that would be needed by anyone who found themselves invading, occupying, administering or simply liaising with the civil authorities there. I bought it (in a library duplicates sale) mostly for what it said about the once very extensive network of minor railways in Luxemburg.