It is an inline, four-cylinder engine of which there are files archived at the Nasm with references under number Doc. (BD-345000-01). Info has been requested.

“Detroit Aeromotor”

-The 30-50 hp Detroit Aeromotor had four cylinders in line as the picture.

-The 60-75 hp Aeromotor had 6 cylinders. Both were water cooled and from 1910.

-In 1919 appeared the "Viking" giving 140 hp, and according to references it was an air-cooled 16-cylinder in X.

From Appendix 10: Builder of water-cooled, 4- and 6-cylinder inline engines.

"General ad of this brand"

-The advertisement is from July 1910 and it already mentioned three aeronautical engines.

-Below we see two of them with propeller, instead of a wheel like the one in the ad, probably for airships.

“Two Detroit Aero Constructions Co.”