Abstract: A coupler mountable on the dipper stick and tilt assembly of a machine including a body provided with a fixed jaw and a pivotal jaw connectable to the mounting pins of an implement; a stop latch pivotally connected to the body, biased in a first position obstructing the removal of a mounting pin disposed in the fixed jaw; a latch cain pivotally connected to the body engageable with the stop latch for pivoting the stop latch upon pivoting the latch cam; a fluid actuated cylinder assembly operative interconnecting the latch cam and the pivotal jaw; and means of cooperable with the cylinder assembly and the latch cam, functional to preclude pivotal movement of the latch cam when the body is disposed in a first orientation, and to permit pivotal movement of the latch cam when the body is disposed in a second orientation.