Lake Cushman, northwest of Shelton in Mason County, Washington, was a favorite topic. Otto's wife Mary and their daughters lived in Lilliwaup, just a few miles away, while he worked in Seattle.
Note the backwards 'S' in Otto's signature. He was writing captions backwards on the glass negatives and sometimes wrote letters without reversing them, so that they are backwards on the postcards.
The lettering of the caption is also unusual because it is black, not the typical white.
This image is courtesy of Will Stuart.
There is also an Image 215 (215 - Oregon Bldg A.Y.P.E.) showing an exhibit hall at the Alaska Yukon Pacific Exposition. Perhaps Otto reused the image number because no one would be interested in an A.Y.P.E. card after the exposition ended.