The siren on the "rocket" knives wasn't actually designed to be mouth blown to operate although they do work that way. You whirled the knife around in the air to operate the siren, the spot where the lanyard attaches keeps the siren to the wind when you whirl it around. Salt Point is a town near Binghamton, N.Y. and around 15 years ago there was an auction there of items from the Rail City tourist attraction where they sold many of these knives, and many of them were still on complete display cards. They are pretty cool mementos of that era of early rocketry and when every boy carried a knife.