Found this on Shorpy.com.
It's a 1929 view of the brand new "Senator" at Washington Union Station.
Engine 5401 seems to have a bit of decoration that I haven't seen before on a Pennsy engine. Note the keystone plates on the valve heads above the pistons. I wonder if they dressed her that way just for this maiden run. Also, note the absence of catenary. This was pre-electrification.
Clicking on the image will enlarge it to its full (enormous) size. I'm pretty sure that freshly scrubbed look will be gone from the train and its engine crew by the time 5401 gives way to a DD1 at Manhattan Transfer.