This shell trumpet has a splendid patina and wear from ritual handling and use.
Such instruments usually are referred to as conch trumpets but the shells used are not conch shells but chank shells (Turbinella pyrum).
The shell has been converted into a trumpet or horn with the removal of the end of the point to provide a blowing hole. A leather strap has been attached and this is fitted with a small spherical white-metal bead and a smaller glass bead.
Such shells are important ritual objects in Tibetan Buddhism. They are used as ceremonial trumpets in prayer rituals, to summon monks to prayer, to summon spirits as well, and to invoke rain and water (Reynolds, 1978, p. 80.) Shanghai Museum (2001, p. 136) illustrates a conch shell trumpet carved with eight small Buddhas which is said to have been a gift from the Qianlong Emperor to the Dalai Lama.
Overall, this is fine example with excellent patina.
References
Lama, M.N. Ritual Objects & Deities: An Iconography on Buddhism & Hinduism, Lama Art, 2003.
Reynolds, V., Tibet: A Lost World: The Newark Museum Collection of Tibetan Art and Ethnology, The American Federation of Arts, 1978.
Shanghai Museum, Treasures from Snow Mountains: Gems of Tibetan Cultural Relics, Shanghai Museum, 2001.