| 1931 ADLER Traffic Signal Casing SAFETY Patent 49307 |
| 1931 DAVIS MICHAEL Alarm Signal Patent Print Art |
| 1931 ADLER Design Traffic Signal Facing Patent 49310 |
| 1931 DELCO REMY CORP Sound Signal Patent Print |
| 1931 SORENSEN Highway Crossing Signal Patent |
| 1931 NAT FIREWORKS INC Marine Signal Patent |
| 1931 BROOKS JOHN Signal Device Patent Print Art |
| 1931 LODER Automatic Signal Whistle Valve Patent |
| 1931 OLSON Light And Signal Switch Patent Print |
| 1931 DRIGGS Ammunition For Signal Pistols Patent |
| 1931 FISHER Design Highway Crossing Signal Patent 49299 |
| 1931 CRITCHFIELD ROBERT Sound Signal Patent |
| 1931 ANDERSON Marine Signal Patent Print Art |
| 1931 CLARK Traffic Signal Indicator Patent Print |
| 1931 KELLEY CECIL Signal Horn Patent Print Art |
| 1931 MITCHELL Umpire'S Signal Jacket Patent |
| 1931 MARINDIN HENRI Signal Horn Patent Print Art |
| 1931 BENNETT Acoustic Signal Mechanism Patent |
| 1931 MOCK Highway Crossing Signal Patent Print |
| 1931 BUCHANAN Football Down Signal Patent Print |
| 1931 WOOD WILLIAM Signal System Patent Print Art |
| 1931 DOMINGO ANGLADA Signal Lamp Patent Print |
| 1931 JOSEPH Automatic Warning Signal Patent |
| 1931 STETSON CHARLES Signal Rocket Patent Print |