American Sanders - Clarke #960125 - Paper Retainer Bolt & Washer combination - OEM product..  Made by American Sanders - Clarke..  The same item that comes with the new Super 7R edgers when new..  Includes cotter pin locking the bolt and washer together.

Note -  this is hardened and comes with the cut in the bolt to help clean out the threads in the shaft when you screw the bolt in.