Interesting to note that the low pressure cylinders were equipped with piston valves, I would think somewhat unusual for Mallets of this vintage.
@RailMix It was built by Santa Fe in 1911 as a Mallet. Photo taken not long after on November 11, 1911. It was cut up in 1917 to build locomotives #3015 with the high pressure truck and #3025 with the low pressure truck.
@r_i_straw OK, it looks like this one had the flexible hinge (for want of a better descriptive) built into the boiler- troublesome and not very successful. I had never seen a 3/4 view of this locomotive so did not recognize it at first.
@RailMix No, the 3000 class had rigid boilers. There were a few Mallets in other classes that had flexible (accordion pleated) boilers that were a maintenance nightmare.