1851. 4 RBS Ferslew. Plate II, no. 30. Wonderful APRIL-COVER (Third day of usage) from Slagelse to København with mute canc. and 1 1/2-ring SLAGELSE 3.4.1851 BOTH IN BRIGHT BLUE COLOUR. Blue ink are very rarly seen from april 1851 and normal only from København. Only Slagelse and Stege are also seen. ONLY TWO COVERS KNOWN. Ex. Schmidt-Andersen, Peer Lorentzen and Borch Jensen. Certs. Møller BPP and Nielsen [ 1 ] [ ✉ ]