According to Art Wallace's book these were 0-6-6T, 42" gauge locomotives of the Covington, Columbus & Black Hills. One of them was #560 and the other was #552, which was the rebuilt 0-6-4T, 36" gauge Stockton & Ione #2. Iowa did have several other Mason bogies running around, but most were standard gauge. One of the 3' gauge 2-8-6T locomotives of the Denver, Utah, & Pacific, went to the Burlington and Northwestern, in Iowa. This locomotive #691 and its twin, #673 were a little smaller than the four DSP&P 2-8-6T locomotives, as they had 15" by 18" cylinders and 36" drivers. The wreck in the photo was on 9-20-1896 and it was another McKinley vs. Bryan staged collisions.
Dave