Don’t think there is a difference between the brackets, but there was a difference between the arm levers. Study this exploded diagram, and you will see the early version had the return spring anchor-point welded to the arm, while later versions had the same function fulfilled by a bracket bolted to the arm.
Larry
![IMG_0570 IMG_0570](https://pantera.infopop.cc/fileSendAction/fcType/0/fcOid/26671146459963349/filePointer/26671146460086949/fodoid/26671146460086945/imageType/MEDIUM/inlineImage/true/IMG_0570.jpeg)