Jim,
this is yet another of the Union Pacific's compact articulated streamline trains. All were built by EMC and Pullman-Standard - the M-10000 and M-10001 in 1934, and M-10002 - M-10006 in 1936.
It must be one out of the "younger"
series. They differed all a little bit, but from the photos I compared with your pic, I think yours must be the M-10005. However Russ is right with the name "City of Denver" (which strangely was also assigned to the M-10006, as it seems - look on
this link. As you see, the M-10003 had no 'City of...'-name, however.
)
Here is the M-10005 at Dupont, CO in 1937
Ron