Thank you! You have hit the bullseye!!! It's a
Piano Hammer Head Smoothing Iron.
That "Tune Piano Supply" storefront in Bonanza also has the answer to another
tool mystery presented by same Flea Market vendor! As he was selling the
"Smoothing Irons" to me, he asked me if I could identify another tool he had.
Thanks to you, I now know that it is a "Piano Hammer Butt Plate Inserter."
Somehow, I just knew that the collective knowledge and wisdom of the Porch would
be able to identify those oddball tools!