You shouldn't have this.
The item id for Kuwait Rattlesnake Suppressor in unturned is 5139. You can use this ID with the commands below to spawn the item, give it to a player or buy it on a modded economy server.
Size_X: 1
Size_Y: 1
Size_Z: 0.125
Silenced:
Volume: 0.9
Ballistic_Drop: 1.4