A little more history....The first narrow gauge locomotive to get lettered with the speed script may have beeen 483 in late 1939. The last unit may have been 463, coming off a long rental to the RGS in late 1943 or early 1944. Other late units may have been 360 and 361 in '43 and 346, then the Durango switcher, about the same time.
The D&RGW had carefully scaled drawings of the heralds. I have a copy of the 1936 herald. Thinfilm decals were made from such drawings and are very accurate, and can be projected.