This is Holbrook Aero Supply in Joplin, Missouri.

-In 1910 they made two water-cooled, inline, four-cylinder engines. One of 35 hp and the other of 50 hp.

-The 35 hp was used on a machine manufactured by HJF.

From Appendix 10: 1910 ad that confirms the existence of this brand that made two engines: 35 and 50 hp.

“Holbrook ad”