Airboat Propellers
This Sensenich airboat propeller shows characteristics of its non-aviation usage.   Notice the broad, flattened blade and squared-off tips.  The aerodynamic design favors a high drag design that is useful for slowing an airboat but undesirable for an airplane.
Sensenich and Banks-Maxwell.
Common Manufacturers:
Identification Help:
Sensenich airboat website information
Stamped numbers seem to be most common as diameter X pitch, for instance "72LXL-40".
Many of these were designed for use with automotive, as well as aircraft, engines.

Go to our Wooden Propeller Forum and post your question in the Propeller Identification forum.  (You will need to register with a username first).