From Brotato Wiki
Item
Hunting Trophy is an in-game item that can be bought from a Shop or can be found in a Crate. Most Items modify the Stats of the player, and some of them provide additional effects.
Hunting Trophy
Hunting Trophy gives you a chance to gain Materials when you kill an enemy by a critical hit. Similar to the Thief Dagger.
Unlike the Materials gained by Harvesting, Hunting Trophies don't give Experience. It only gives you the Currency Part of Materials.
Stacking
When an enemy is killed with critical hit, for each Hunting Trophy the character has, the game rolls a 33% chance to give 1 materials (Just money, no XP, so lets call it gold). If there are 2 hunting trophies, it rolls twice. If there are 3, it rolls the 33% chance 3 times.
For each succeaful roll, you are given 1 gold. If there are 2 Hunting trophies, it can give 2 gold with 1/9 chance, it can give 1 gold with 4/9 chance, and not give any with 4/9 chance.
If there are 3, it could give 0 to 3 gold depending on chances.
The result is that the average amount of gold earned is doubled if you have two, trippled if you have three.