Herren Aeronautical Corp was a company from Chicago that in 1929 prepaired the aeronautical construction and engines but of which details are not known.

From Appendix 6: In the main text this mark is mentioned but without details or illustrations.

-Now we have found the engine and we can see its shape. It is built by Herren Aeronautical Corp. with the intention of offering a small plane for "poor" men. The engine consumed auto fuel.

“The affordable Herren airplane”

-Below we can see the engine's appearance with its four radial cylinders in X, two-stroke, and air cooled.

-It has reduction gear and a small supercharger. It measures 23 inches in diameter and gave 58 hp.

“Nice picture of the Herren engine”