The use of mouth-blown glass balls as floats for fishing nets dates back to at least the mid 1800's. By the early 1900's they were in use around the world. It is widely believed that the Japanese produced more glass fishing floats than any other country.
Glass fishing floats (also called seine balls*) come in a variety of colors, sizes, and shapes and are widely collected, often fetching hundreds of dollars or more for a single float. The presence of a maker's mark, unique colors, large sizes and other attributes can significantly increase a float's value.
Thanks to prevalent ocean currents, many Japanese floats make the multi-year voyage across the Pacific and end up on Hawaiian and Californian beaches.
*A seine is a large net with weights along one edge and floats along another.