Nearly all of Otto's own photos of the 1909 World's Fair, the Alaska Yukon Pacific Exposition, have images in the range from 200 to 299. There are non-A.Y.P.E. images in this range as well, and sometimes their image numbers match A.Y.P.E. image numbers. This suggests he reused the numbers after the exposition ended; presumably no one would want to buy A.Y.P.E. postcards then. Images in the range from 200 to 299 of downtown Seattle which show the Smith Tower also support this theory - it was completed in 1914.
Decades with images:
A selected image from the range 200-299: