| 1931 UNION SWITCH SIGNAL CO Electrical Signaling |
| 1931 ADLER Traffic Signal Casing SAFETY Patent 49307 |
| 1931 MUELLER Automatic Hydraulic Crossing Signal |
| 1931 UNION SWITCH SIGNAL CO Railway Signaling System |
| 1931 GEN RAILWAY SIGNAL CO Signaling System Railroads |
| 1931 DAVIS MICHAEL Alarm Signal Patent Print Art |
| 1931 ADLER Design Traffic Signal Facing Patent 49310 |
| 1931 UNION SWITCH SIGNAL CO Electric Train Signaling |
| 1931 UNION SWITCH SIGNAL CO Signaling Art Print |
| 1931 UNION SWITCH SIGNAL CO Power Supply System |
| 1931 DELCO REMY CORP Sound Signal Patent Print |
| 1931 UNION SWITCH SIGNAL CO Remote Control Art |
| 1931 UNION SWITCH SIGNAL CO Railway Track Circuits |
| 1931 SORENSEN Highway Crossing Signal Patent |
| 1931 UNION SWITCH SIGNAL CO Railway Switch Controlling |
| 1931 MOTO METER GAUGE EQUIP CORP Signal Horn Art |
| 1931 UNION SWITCH SIGNAL CO Wheel Counting Art |
| 1931 GEN RAILWAY SIGNAL CO Track Instrument Art |
| 1931 NAT FIREWORKS INC Marine Signal Patent |
| 1931 BROOKS JOHN Signal Device Patent Print Art |
| 1931 LODER Automatic Signal Whistle Valve Patent |
| 1931 UNION SWITCH SIGNAL CO Railway Switch Operating |
| 1931 OLSON Light And Signal Switch Patent Print |
| 1931 WOLF SAFETY LAMP AM Signal Lamp Art Print |
| 1931 UNION SWITCH SIGNAL CO Train Indicating |
| 1931 DRIGGS Ammunition For Signal Pistols Patent |
| 1931 WESTINGHOUSE AIR BRAKE CO Signal Horn Art |
| 1931 FISHER Design Highway Crossing Signal Patent 49299 |
| 1931 KING Testing Railroad Signal Systems Art |
| 1931 MOTO Acoustic Signal Mechanism Art Print |
| 1931 CRITCHFIELD ROBERT Sound Signal Patent |
| 1931 UNION SWITCH SIGNAL CO Motor Control Art |
| 1931 WILLING Light Signal System Railroads Art |
| 1931 ANDERSON Marine Signal Patent Print Art |
| 1931 CLARK Traffic Signal Indicator Patent Print |
| 1931 GEN RAILWAY SIGNAL CO Interlocking Railroads |
| 1931 UNION SWITCH SIGNAL CO Electrical Art |
| 1931 UNION SWITCH SIGNAL CO Time Release Mechanism |
| 1931 KELLEY CECIL Signal Horn Patent Print Art |
| 1931 UNION SWITCH SIGNAL CO Electrical Translating |
| 1931 JAMES Signal Switch For Trolley Lines Art |
| 1931 GEN Light Signal System Railroads Art Print |
| 1931 MITCHELL Umpire'S Signal Jacket Patent |
| 1931 UNION SWITCH SIGNAL CO Railway Track Circuit |
| 1931 AUTOMOBILE Automatic Warning Signal Art |
| 1931 UNION SWITCH SIGNAL CO Track Rail Contactor |
| 1931 MARINDIN HENRI Signal Horn Patent Print Art |
| 1931 CHASE Testing Railroad Signal Systems Art |
| 1931 UNION SWITCH SIGNAL CO Railway Car Retarder |
| 1931 PHELPS Traffic Signal Indicator Automobiles |
| 1931 UNION SWITCH SIGNAL CO Railway Traffic Governing |
| 1931 BENNETT Acoustic Signal Mechanism Patent |
| 1931 MOCK Highway Crossing Signal Patent Print |
| 1931 BUCHANAN Football Down Signal Patent Print |
| 1931 UNION SWITCH SIGNAL CO Highway Crossing Signal |
| 1931 E Synchronous Motor Electric Audible Signal Clock |
| 1931 WOOD WILLIAM Signal System Patent Print Art |
| 1931 DOMINGO ANGLADA Signal Lamp Patent Print |
| 1931 RICHTERKESSING Electric Signal System Art |
| 1931 JOSEPH Automatic Warning Signal Patent |
| 1931 UNION SWITCH SIGNAL CO Electrical Controlling |
| 1931 GEN RAILWAY SIGNAL CO Railway Track Circuit |
| 1931 UNION SWITCH SIGNAL CO Railway Signaling |
| 1931 UNION SWITCH SIGNAL CO Measuring Time Intervals |
| 1931 STETSON CHARLES Signal Rocket Patent Print |
| 1931 UNION SWITCH SIGNAL CO Railway Interlocking |
| 1931 SUBMARINE SIGNAL CO Method Means Watch Regulation |
| 1931 GEN RAILWAY SIGNAL CO Switch Machine Railroads |
| 1931 UNION SWITCH SIGNAL CO Highway Crossing Protection |
| 1931 CHEATHAM Electric Signal System Art Print |
| Ertl/Scale Models 1931 International "SIGNAL" Fuel Tank |
| 1931 Gamewell Peerless fire alarm signal box photo ad |