This striking United Nations 1977 Water Conference pair highlights the global call for sustainable water management during the UN’s first major water summit in Mar del Plata. Each stamp features a bold, modernist design of stylized water droplets flowing into a funnel—symbolizing conservation, purification, and shared responsibility. The 13c (yellow background) and 25c (coral background) values form a complementary duo, both bearing the UN emblem and clean typographic layout. A desirable thematic pair for collectors of UN issues, environmental topics, and 1970s design.