indestro socket set

[jimwrench]

 Have a Indestro socket set which contains one oddball socket. It has a conical internal knurled surface. Can someone give me use of this socket ? This is 1/4 hex drive set. Driver is stamped(Indestro Mfg Corp Chicago Pat pend) Anyone have approx date on manufacture ? Can't seem to include picture as error message says file too large even with only one photo. Maybe someone will recognize usage from description till I find what I'm doing wrong.

[keykeeper]

That is for removing rounded off nuts. I have one of these sets I got from bonneyman, and it has one I believe. I love these little 1/4 hex drive sets. Very neat.