Shepherd's whistle
They are also produced commercially. Simple whistles may cost less than 1 USD in bulk; expensive ones may be quite ornate. They are commonly made of plastic, aluminum, stainless steel, silver, brass, titanium, Corian, jade, buffalo horn and other materials.
Avner Strauss
During the years Strauss devoted many years to the research of catalogs and collecting whistles, he published hundreds of articles about the subject and about the History of whistle manufacturers in the 19th century and is considered one of the world's foremost authorities on the subject of collecting whistles, some of his articles and samples of his collection which might be the largest known, can be found on the Whistle Museum.