WWII German U-Boat ‘Karten der Harmonischen Gezeitenkonstanten fur das gebiet der Westbritischen Gewasser’ Book containing 20 pages of ‘Harmonic Constant’ tidal charts of the West Coast of Britain and Ireland showing the same area of water with differing states of tidal flows, issued by German Kreigsmarine to German U-Boats, numbered Pruf-nr. 0540, 42cm x 31cm.