Patent # 3574381, but very vague as to what it does and no reference to the square drive.  Didn't measure the size of the drive, but looks to be 1/4".  Photos when the server unloads......

DM&FS

This gave me the knowledge to tell a friend.

Boomer:  Check the other post about the 1/4" drive gripper.  I forgot I posted this one w/ no pix due to the server issues.  The other post has links to photos and I'm having issues deleting this post...  I hope you'll understand.....

DM&FS