The one in thread 12 is identical to the ones we made during our apprenticeships. And I've still got it! 54 years and still going strong.
It ensures that a) it will only go into the hole in the grip square on and b) that the nut sits on the tool absolutely square and c) it will do both the outer and inner nut.
These old time Armourers have got to get up to date and get out a bit more haven't they........?