I have a collection of old farm implement wrenches and came across this one last week.  Have not seen one like it before.  The only marking is "D4".  Anyone know what it might be?

There is a fellow comes in here time to time, well versed in the MVTCA, Missouri Valley Tool Collectors,   those guys specialize in farm equipment wrenches.  There were dozens of manufacturers, making dozens of machines, each having its own special wrenches.  Good luck

There's another one categorized as "orphan"  -- box lot 75 (9) on the 2017 Spring Wrenchingnews auction.
( http://wrenchingnews.com/2017-york-auction/photos/S17-cb075-77.jpg )