What a treasure Tom!
Osthaus painted the portrait of the winners of the National Field Trial Association for the first thirty years of the Championship, and the images were reproduced as calendars and lithographs by the Du Pont company in the early 1900's.
The 1916 series included portraits of every Field Trial Champion; Count Gladstone IV in 1896 through Manitoba Rap in 1910
He also did "Hunting Dogs" for Austin Powder Co.
More on Osthaus here
http://www.picturetrail.com/sfx/album/view/20832819