TRUTH CASEMENT OPERATOR

IS IT POSSIBLE TO TELL ME WHAT REPLACEMENT OPERATOR I WOULD NEED? ON THE BACK IS THE # 7 IN THE MIDDLE ON THE BACK IS THE #34 AND ON THE RIGHT IS STAMPED LH. THE U.S. PAT.4505601 IS STAMPED ON THE BACK AS WELL. THE ARM IS LABELED TRUTH. THE ARE IS 9 1/2" FROM THE CENTER OF THE GEAR TO THE CENTER OF THE ROLLER. THE SCREW HOLES ARE 3" ON CENTER AND 1 5/8" ON CENTER. THANK YOU FRO ANY HELP YOU CAN GIVE ME.