Newton made at least two different models of the mower, a “J” and an “L”. It was the “J” that was used on the jeep (according to the ad). (See brochures for the Newton and other mowers here)
“THIS IS AN ORIGINAL 1948 ADVERTISEMENT FOR THE NEWTON POWER SICKLE MOWER; FITS TRACTORS AND JEEPS; MANUFACTURED BY THE H. G. & S. MANUFACTURING CORPORATION IN NEWTON, WISCONSIN. AD IS IN GREAT CONDITION AND HAS EXCELLENT GRAPHICS. AD MEASURES 5 1/8″ X 3 5/8″.”