Think you could be right. This image from a Perkins SL5 on an Ebay listing, has the nose piece fitted 90 degrees round but also has a different number of teeth. Apart from that it does look identical. Presumably just affects access to the cable terminals
Anyone out there know if the Cole Cranes used any engines that had SL5 type starter motors and, if so, what engine was it? I have a starter that is supposed to have been for a Cole Crane but can't find anything on the net to confirm.