Fantastic! No finishing needed, very loud! I can pretend to be a Netball Teacher at last! Printed this whistle tonight with metallic PLA, with Flashforge Adventurer 3, using https://www.amazon.co.uk/gp/product/B07D7SYS7J/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1, Shiny Gold from Amazon. I think the metallic filament might add to the fabulous overtones of the whistle sound!
FlashForge Adventurer 3
No finishing required, very loud! No internal ball.