This 'Mini Ball' measures 5 3/4 inches in circumference or about 1 3/4 inches in diameter.
It has a partial stamp of WP #10 'Rivermouth' in a triangular configuration. Pretty hard get the whole stamp on a seal button this small.
Mini balls are uncommon; ones with marks are even rarer.
This netted float is a fine example of a mini ball.
Found in Hawaii.