5c blue on salmon 'Seebeck' postal stationery envelope (H&G B19) used with RIVAS cds dated 9 MAR. Addressed to LIBERIA, COSTA RICA with LIBERIA arrival cds dated 11 MAR on front. Unclaimed with manuscript 'No ce connu' and returned with second LIBERIA cds in purple dated 14 AUG and RIVAS arrival cds on reverse dated 16 AUG. Very unusual.