I should have written this post earlier but I was busy. So better late than never.
Thanks to all of you that supplied me with all these precious infos and helped me answer the questions I was having on this gun

A special thanks to Philip for his very detailed explanations.
For the ones that could be interested, I displayed hereafter the photos of one of the recent addition to my collection.
It's a very nice and old Taiwan aborigines knife (65cm long) from the Atayal tribe, north of the island.
Best,
Yuanzhumin