My understanding is this:
Steering wheels changed a lot in the time period when the W111 finny was first developed. The earliest before coupes and cabs (also shared with Ponton cars), had the non-padded center, circular horn ring with ridges. The horn ring also acted as the turn signal when rotated and the ridges were finger grips. This ring does not have the two holes on either side of the steering wheel spoke.
The next version on the last Ponton and early W111 coupes/cabs had a padded center, circular horn ring with no ridges. This ring had the two holes in the steering wheel spoke and did NOT work as a turn signal. Early W113 had this as well.
The next version had a different padded center and a flattened horn ring again with no ridges and had the collapsible steering column.