This was all discussed in 2009. As I recall from the thread, you were the only one who was "sure" that "Cap" meant Clarke in this case. "Cap" could also be the name of a fishing guide - far more likely given the gross dissimilarity of the faces. It could also refer to a location, like "Cap River."
Regardless of what was written on the back of the photo (a major source of fraud in the hobby) and what the handwriting folks may say about who wrote it (they are not always right), letting that trump major differences in skull stucture and facial features (none of which you have been able to explain) is an unwise pratice.
Note also that we have a lot of photos that were for sure annotated by major figures (like Spalding and McGreevy for example) that are loaded with ID errors.
You might do well to read pages 1 and 2 of
http://sabr.box.com/shared/static/10...092a683653.pdf
Even if it doesn't help you , it may help others. Keep in mind that you are claiming that these 2 guys are the same person: