https://www.datamp.org/ Recently added patents en-us https://www.datamp.org/patents/displayPatent.php?id=85997&pn=548,615 Improvements relating to male spanners for use with a screw having a non-circular recess to receive the spanner Patentee: Leslie Lionel Long - Coventry, Warwickshire England Granted:1942-10-16

Rounded end, and circumferential groove combine to allow a driver to turn a "hollow head" screw or bolt even when not in direct line. The drawings show the principle applied to a hex "Allen wrench" type tool; decades later a similar device was patented and marketed as "ball driver."
This is one of 85,286 patents currently in the database at datamp.org

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