The threads look like they may fit a steel barrel? don't have one handy to try it.

Huh. I've never seen one of those on a barrel before. Never seen one anywhere else though either.

They made more than one, someone else is wondering what it is for.
https://www.etsy.com/listing/469259692/vintage-threaded-iron-industrial-handle?ga_order=most_relevant&ga_search_type=vintage&ga_view_type=gallery&ga_search_query=oil+drum&ref=sr_gallery-1-9&organic_search_click=1

Pg 3 of the Sept. 2009  MVWC NEwsletter  shows the drawing for  patent 2,543,151 ( http://www.datamp.org/patents/displayPatent.php?number=2543151&typeCode=0 )  Combination Bung Plug & Agitator Crank.   The crank  was for an agitator inside a steel barrel, to stir the contents before pouring some out.  The threaded portion fit the "bung" opening that had the stud end of the internal agitator.

Thank you that nails it down!

Yay!