From Brotato Wiki
Hunting Trophy is an in-game item that can be bought from Shop or can be found in a Crate. Most Items increase the Stats of the player while some of them provide unique effects.
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.
When an enemy is killed with critical hit, for each Hunting Trophy the character has, the game rolls a 33% chance to drop 1 material. If there are 2 hunting trophies, it rolls twice. If there are 10, it rolls the 33% chance 10 times.
For each succeaful roll, you are given 1 material. If there are 2 Hunting trophies, it can drop 2 coins with 1/9 chance, it can drop 1 coin with 4/9 chance, and not drop any with 4/9 chance.
If there are 3, it could drop 0 to 3 coins depending on chances.
The result is that the average amount of gold earned is doubled if you have two, trippled if you have three and so on.