Surfacing propellers, i.e. propellers specially adapted for operation at the water surface

Official title: {Surfacing propellers, i.e. propellers specially adapted for operation at the water surface, with blades incompletely submerged, or piercing the water surface from above in the course of each revolution}

B63H2001/185 (Surfacing propellers, i.e. propellers specially adapted for operation at the water surface) appears on 100 US grants and 64 published applications in this corpus.