1990s British MOD/Special Forces Issue Lightweight Emergency Distress/Signalling Perry Whistle. Dark blue. Made in England by R. Perry & Co. Ltd, Birkenhead. NATO Stock Number (NSN): 22C/4220-99-130-2489. New Old Stock. Lightweight signalling aid. Loud dual frequency selected to be discernable from general background noise. Low noise attenuation for carrying long distances. Operates at half normal lung pressure to ensure effective use even when suffering from breathing problems, e.g. hypothermia, injury. Suitable for use on life-jackets. Made from high specification tough shatterproof plastic that will not adhere to skin in sub-zero-temperatures. No moving parts - functions when wet. Lanyard hole. SOS Morse code aide-memoire. Please see the photographs. Listing is for one whistle; no extra postage charged for additional whistles.