I don't think I've seen this particular photo before. A very nice picture of a 56 btw.
Class 56 engines do appear in a lot of photos from the 1880's-90's. The first Class 56 (#24, later #41) and the first Class 60 (#22, later #228) came from Baldwin in 1877. #24 was judged easier on the track so a large number of Class 56 were ordered in 1878-80, large purchases of Class 60 didn't come until 1881-82. There were about the same number of Class 56 engines as there were of the Baldwin built Class 60's so if somebody took a picture of freight in the 80's or 90's it was quite likely to have a 56 on the point.
Class 56 was being sold off by the late 1890's and most of them were scrapped in 1908. A few survivors, most of them converted 0-8-0 for switching use, hung on until 1916-17 when they went off the roster. I don't recall ever seeing a picture of one as an 0-8-0. Some that had been sold to logging lines survived until the late 1920's. I've always regretted that none made it to modern times, altho DSP&P 51 (Baldwin 1880) now at CRRM is essentially the same type.
There are a bunch of early D&RG (and DSP&P) engine classes that I wish we had an example of.
hank