Our Remnant: From the Ashes Pocket Watch Guide features the exact way to obtain this secret amulet! If you're looking to obtain a quality amulet for yourself that helps increase your stamina gain and reduces your stamina cost, then this is one of the best do it!
Pocket Watch Description
Increases Stamina Regen by 15 per second and reduces Stamina Cost by 15%
"They say love's stronger than anything. Brabus don't say that, but then Brabus has forgotten a lot of things he once knew."
How-to Get the Pocket Watch
You will need to have completed the first dungeon/boss in the game and unlock Mud Tooth's Hideout. This can be found in Ward 13. Once you travel here, you should see a crashed helicopter in a huge tree!
There are some stairs nearby this tree, go ahead and run up them towards the helicopter. Go inside the helicopter and you will see an NPC named Mud Tooth. Talk to him and he will offer you some wares for sale, like an Ammo Box, Mudtooth's Stew, and Mudtooth's Tonic. You can sell things to him as well.
Now that you are here, all you'll need to do is listen to the old guy ramble on with some stories. He's got an option that will be something in the nature of, "Got any more stories to share?" Just keep clicking on that and "No, tell me more!" when he's done telling one of his stories. This will last in the area of 10 minutes or so, and once he's told his final story he will hand over the Pocket Watch!
Keep in mind that this NPC isn't a guaranteed spawn. You might need to re-roll your world to get him in the game.