This is one of a series of images of Mt. Rainier. Many were numbered with an 'R'.
The image number is visible near the right side of the postcard, about halfway up. The image is not signed on the front but has Otto's imprint on the back.
There is also an Image 1 (1 - A Cedar Tree in Washington - Circumference 67 Feet) and an Image X1 (X1 - Bason A.Y.P.E. Grounds). Reuse of image numbers and different image series make it difficult to know how many images Otto published.