Acme Whistle 649 에크미휘슬 Life saving/rescue whistle.
S.O.L.A.S. approved, British Admiralty and NATO approved. 
For carrying dual frequency designed to stand out from background noise. 
Will not adhere to the skin in sub-zero temperatures. 
Tough construction, food grade shatterproof plastic. 

Easily blown, important if you are young, elderly, injured or cold.