Brass key carabiner. Obviously not suited for climbing, etc.
The nice thing about brass is that its a "living" surface, meaning it changes with time. High wear areas will polish up to shiny brass, low wear areas will keep the patina, bare areas will be affected by its environment...what colors form depends on your body chemistry and exposure....browns, blacks, green, blues, etc are all possible.
This is an item we purchased to modify and/or resell, we didn't manufacture it.