Most unusual! It kinda reminds me of a set of nutcrackers, only with three arms
It must be a very rare,"mutant nutcracker". In use it might be difficult to use although by utilizing the two handles(one in each hand)a lot(maybe too much)of force could be applied to a stubborn screw.
I came across this one awhile back and thought it a bit unique.Quality construction and a patent date of Dec 18 1917