10 MPH is probably a start from a stop on the grade, likely meeting an eastbound at west Plain, just about 2-3 tenths of a mile east of this point. The 303 was built in 1910 with 20x28" cylinders, 63" drivers and total engine weight of 215,000 lbs; she was rated only 34,150 lbs tractive effort. On the serpentine, unrelenting westbound 2% grade to Moffat Tunnel, the 303 was rated 530 tons, and with 4 big heavyweights on the drawbar, she was pretty well near her limit. 10 MPH from a start wouldn't be terrible, but this territory was only rated 18 MPH freight/23 MPH passenger, per the 1937 D&SL employee timetable. Today it's 25/28 MPH, so only modestly improved speeds with the improved physical plant. There could have been a slow order over the trestle, but the ETT did not discuss any trestle speed restrictions. The next known slow order would be at the site of old tunnel 9 about a mile and a half further west at MP 27, 5 MPH permanent.
2015 in Santa Fe, New Mexico. His/her position was much higher than mine. Hiroshi Nakanishi | Boxcar Red Collection
I believe that there were two different depots. The building to the left was for the Rio Grande and the one on the right was the Santa Fe.