Matt doesn't give Grudie back his brass knuckles in the Longbranch but later he knocks Chester out with a set.
Maybe it was because it was done by dark of night; but that night, with Grudie's back to his Pa he dug through his pack and pulled out another set of shiny brass knuckles. Even at the end when Pa chucked Grudie's second set of brass knuckles away, Grudie probably has a third set hidden somewhere in the wagon.
Strange sounds can be heard off screen as Dehner, Jackson, and Doyle climb onto the wagon bench. Sounds like metallic equipment being dropped or knocked over. The sound gets so loud that all three actors turn to their left and look off and to the back of the wagon with puzzled looks. They recovered their composure quickly back to character and moved the wagon on like nothing had happened.