The Victorinox whistle is a scale tool found only in the 58mm Whistle model.
The special scale is about twice the thickness of the regular scale, with a hole at one end where one blows, and an opening on top part for the air to escape and produce the whistle sound.
The whistle was designed by Davison Innovations. The information below was supplied by that company.
A link is available to their website: The Swiss Army Whistle Knife.
In 1997, our client from California hired us to create an alarm to call attention in an emergency situation, to integrate into a survival knife. The Davison Design and Development team of Inventionmen™ researched and found that an alarm built into a small knife could not be 100% reliable in an emergency situation, it increased manufacturing cost and required the consumer to purchase batteries. In addition, the batteries would increase weight and size of the knife.
The Inventionmen™ applied Davison Design and Development's exclusive Inventegration™ process and presented our client with an alternative solution; installing a sounding device with an extremely loud whistle (102db). It was engineered to fit over the existing knife frame of the most popular knife in Victorinox's brand. The design eliminated electronics and batteries, making the whistle lung powered. Its housing was a cost-effective bet for Victorinox. Not only did it fit the existing knife in usefulness, it literally fit the existing knife. The company had no need to change its manufacturing process. It simply exchanged one housing for another equipped with a whistle, offering a simple method of locating hikers and military personnel, as well as providing an alert system for emergency situations. This achievement by Davison Design and Development's Inventionmen™ was patented (US Patent # 6619225), has been on the market since 1997 and is still going strong.
US Patent Link: Here
Editors Note: Victorinox stopped manufacturing this tool and the associated Whistle model between 2008 and 2015 (ref. catalogues for those years).
See also: The Wenger Whistle