An engine that was built by Holbrook Aero Supply. It was a four-cylinder inline, with 35 hp.

-At the Nasm there is a file with photographs under dossier (BD-20000-01). (Monnett).

-It figures as De Chenne mounted on the De Chenne from 1911, 50 HP.

From Appendix 10: Pioneer constructor of aircraft in the US, we know a 35 hp engine that shows this brand,  and had a price of 650 USD at the time (September 1910, date of the ad below).
 

"De Chene ad for an engine supplied by Holbrook"

-More information in the NASM files.