I had some casual notes on JKPM from research for a another project (including notes on his alias, and the occasional confusion about his initials (James Knox Polk Miller--I've seen him mentioned as "James K. P. Miller" and "James P. K. Miller"--and I mixed them up too). I checked several bibliographies and indexes of books I already had out for other projects. I poked around some on some genealogy websites to make sure I had the correct dates, and had separated out the Alabaman of the same name. I'd noticed the photograph recently in a couple of works while doing some reading on the Black Hills 1860-1910.
My guesstimate on tracing the pic to the year is based on several points. I don't recall the books I saw the photo in, but I have a list of what I read and could go back and check. Hopefully the photographer could be identified, leading to info on where it was shot, or when. Once the locale is identified, there are a couple of approaches to breaking out the year (and possibly the actual site of the photo--always fun when you can do that). And if a decent scan of the original or negative could be found, a lot more detail could be pulled out!
I think it would also be worthwhile to check the newspaper files for Salt Lake City, Virginia City, Bannack, Deadwood, Lead, and maybe Belle Fourche. Probably worth contacting several local historical societies requesting info as well. From there it becomes a matter of following up leads until curiosity is satisfied.