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.
W Dowler &amp; Sons
The Dowler family was engaged in the brass founding business since the late-18th century and had been making whistles since the early 1860s at least. In 1876, the company was named after William Dowler, following protracted legal fights concerning inheritance between the brothers George and William Dowler.