This image is unsigned but has Otto's distinctive writing. He took many photos of the Golden Potlatch parades held from 1911 to 1913; not all of them were signed. This float appears in a V.S. Waters postcard that was postmarked in 1911, so it was part of the 1911 Golden Potlatch.
The white streak running down the center of the image is a tape or cord draped over the top of the roof of the float.
The '4' in the image number is upside down.