Take a good look at the ends on this tool set..
Bought this over the past weekend...for $2...I think...
Got to looking at those ends a bit...have seen that sort of thing before...decided to try a theory out...
Perfect fit, and locks in place...on a Stanley YANKEE No. 130A
Looks like I now have a nut driver for my Yankee screwdrivers...
These have hollow shafts, to allow a bolt to run up into..
Imagine that....