| Electro-Motive Division | ||
| SC | Six-hundred h.p., Cast frame | |
| SW | Six-hundred h.p., Welded frame | |
| NC | Nine-hundred h.p., Cast frame | |
| NW | Nine-hundred h.p., Welded frame | |
| E | Eighteen-hundred h.p. | |
| F | Fourteen-hundred h.p. | |
| TR | Transfer | |
| BL | Branch Line | |
| GP | General Purpose | |
| SD | Special Duty | |
| F | Full-width carbody (as in F40) | |
| DD | D-D wheel alignment | |
| MP | Multi-Purpose | |
| General Electric | ||
| U | Universal | |
| B | B-B wheel arrangement | |
| C | C-C wheel arrangement | |
| P | Passenger | |
| AC | Alternating Current | |
| Fairbanks- Morse | ||
| H | Hood carbody | |
| CFA | Consolidation Line (C-Line), Freight, A-unit | |
| CPA | C-Line, Passenger, A-unit | |
| Alco/MLW | ||
| HH | High Hood | |
| DL | Diesel Locomotive | |
| S | Switcher | |
| T | Transfer | |
| FA | Freight, A-unit (FB indicates Freight, B-unit) | |
| PA | Passenger, A-unit | |
| RS | Road-Switcher | |
| C | Century | |
| M | Montreal Locomotive Works | |
| Baldwin | ||
| VO | Model VO engine | |
| DS | Diesel Switcher | |
| S | Switcher | |
| DRS | Diesel Road-Switcher | |
| RS | Road-Switcher | |
| AS | All-Service | |
| DR | Diesel Road | |
| RF | Road Freight |