Over the weekend I tore apart two similar Chrysler distributors. The advance plates are stamped 13L and 15R. I understand that the digits denote degrees (half of the crank degrees), and I presume that the R and L denote right or left engine rotation direction. What I don’t understand is WHY the rotation direction is indicated. As far as I can tell the components are identical aside from the slot lengths. What am I missing here?