Seal with Knob in the Shape of a Turtle

Seal with knob in the shape of a turtle by Unknown. Dark gray or black stone or metal seal with a rectangular base and a turtle on top. The turtle is facing left and has a large shell on its back with visible lines and texture. The turtle has four legs visible, two at the front and two at the back. There is a cylindrical hole in the base underneath the turtle. The base has a rough texture with visible scratches and marks on its surface. The background of the image is a plain light grey color.