United States Siren Whistle with Chain

By the winter of 1914, fighting on the Western Front ground down to a defensive battle of attrition with both sides digging vast networks of fortified trenches. Soldiers living in the front line trenches faced many dangers, including enemy sniper fire and chemical gas attacks. To overcome these dangers, specific tools were created to limit their effectiveness. Soldiers used trench periscopes to observe the battlefield without exposing their heads to enemy snipers. Gas masks offered some protection against chemical attacks. Hand-cranked gas alarms and siren whistles gave soldiers wearing a gas mask the ability to warn other of an oncoming chemical attack. 

Siren whistle with chain.