another Piston ID question

Anyone recognize these? they are 318 pop-ups .030 over, have L and R on the tops, 2 equal valve reliefs, have 2 F's on the pin side, and inside they say 147 and "HY-DUTY" inside as well as an "H" with a dot. Nothing under the pin. Look cast from inside mold marks. Rough marks are discolorations from moisture/shelf life. Never installed.