Hi Dean,
At first, the D&RG had no number series related to classes.
The best reference I have seen is "Locomotives of the Rio Grande" by the Colorado RR Museum.
The first 100-odd locomotive numbers were all mixed up. For instance:
1 : 2-4-0 class 25 "Montezuna"
2 : 2-6-0 class 35 "Tabi-Wathi"
3 : 2-6-0 class 35 "Show-Wa-No"
4 : 2-4-0 class 25 "Cortez"
5 : 2-6-0 class 35 "Ouray"
6 : 2-4-0 class 25 "Ute"
7 : 2-4-0 class 25 "Del Monte"
8 : 2-6-0 class 35 "Arkansas"
9 : 2-6-0 class 35 "Huerfano"
Have fun.
Doug vV