At a recent photo show I spotted this lovely stereograph and bought it for my collection. These types of images are double pictures taken with a binocular camera that captured two slightly different images of the same view. You then used a viewer to make the scene appear 3-D. These double images were primarily for amusement. You could purchase scenes of places you’d visited (or would like to) or together with friends act out scenes the tableau in card with allegorical and literary themes.
Library of Congress picture collection has several.
The deep yellow card stock of this view combined with her hair style and clothing suggests a date in the 1870s. Weller died in 1878. In the 1880s, it's likely the family sold his negatives. His pictures began to be published by the Littleton View Company, and later, by the major producer of stereo views, Underwood & Underwood.
I'm not sure who's depicted in this image. I know that Weller photographed his daughter, but she's too young to be the woman in this picture. Since the theme of it is "to my Valentine." I wonder if this is his wife, Janette.