| 1931 GILSON Railway Traffic Controlling Art |
| 1931 ALLEN Railway Traffic Controlling Art |
| 1931 MCCANN Railway Traffic Controlling Art |
| 1931 BRYAN Railway Traffic Controlling Art |
| 1931 SORENSEN Railway Traffic Controlling Art |
| 1931 LEWIS Railway Traffic Controlling Art |
| 1931 UNION Railway Traffic Controlling Art |
| 1931 O'HAGAN Railway Traffic Controlling Art |
| 1931 BOSSART Railway Traffic Controlling Art |
| 1931 GRONDAHL Railway Traffic Controlling Art |
| 1931 COLEMAN Railway Traffic Controlling Art |
| 1931 FAILOR Railway Traffic Controlling Art |
| 1931 YOUNG Railway Traffic Controlling Art |
| 1931 STOLTZ Railway Traffic Controlling Art |
| 1931 JACKEL Railway Traffic Controlling Art |
| 1931 SPRAY Railway Traffic Controlling Art |
| 1931 WALLACE Railway Traffic Controlling Art |
| 1931 JOHNSTON Railway Traffic Controlling Art |
| 1931 GEIGER Railway Traffic Controlling Art |
| 1931 THOMPSON Railway Traffic Controlling Art |
| 1931 GEN Traffic Controlling System Railroads |
| 1931 WIGHT Railway Traffic Controlling System |
| 1931 PENROD Railway Traffic Controlling Art |
| 1931 CARTER Railway Traffic Controlling System |
| 1931 BAUGHMAN Railway Traffic Controlling Art |
| 1931 GODFREY Railway Traffic Controlling Art |
| 1931 NICHOLSON Railway Traffic Controlling Art |
| 1931 RUDOLPH Railway Traffic Controlling Art |
| 1931 ANDREW Traffic Controlling System Railroads |
| 1931 GEN Railway Traffic Controlling System Art |