Unaddressed airmail cover with printed '20.IV.75 Visita de la expedicion B.F.S. Biol-Fisica-Suizo ISLA DEL COCO COSTA RICA' Pirate & Treasure Map cachet in black franked with set of three '16th Convention of Radio Amateurs Federation of Central America' issue (SG 998/1000) tied by PUNTARENAS cds's dated MAY 15 1975 with 'M.N. STELLA MARIS' Shark cachet in blue also on front and signed by the expedition members on reverse.