Pictures courtesy of our friend down-under, Dennis.....

Here's the mud retainer ring deriveted from the timing cover. Note those rivet pins. Some POs when doing this job are lazy and they just knock them back into the sump and leave them there! When they do the job
in situ.
Better if you can remove the timing cover and do a proper job.

So you drill out the holes...

Then you tap out the holes...for 3/16" W screws

Job finished with the new retaining ring screws in place.
All ready to be refitted to the block and the new crank seal pressed carefully home.
This mod should make replacing the seal much easier in the future.