| 1931 MCWHIRTER Railway Switch Operating Art |
| 1931 EDWARD Pneumatic Power Door Operating Installation |
| 1931 FIRM ATLAS WERKE AG Operating Bulkhead Doors |
| 1931 HARLEIGH Clock Operating Mechanism Patent |
| 1931 BROWN Gate Operating Means Patent Print Art |
| 1931 EUCLID CRANE HOIST Dump Wagon Door Operating Gear |
| 1931 DALZELL Railway Switch Operating Art Print |
| 1931 LYDA Davit Operating Means Art Print |
| 1931 STREICH Dump Body Door Operating Mechanism |
| 1931 INTERNAT DAVIT CORP Davit Operating Means |
| 1931 COUPLAND Operating Mechanism Machine Guns |
| 1931 GEORGE Valve Operating Mechanism Tanks Art |
| 1931 UNION SWITCH SIGNAL CO Railway Switch Operating |
| 1931 MCCANN Breech Block Operating Mechanism Art |
| 1931 BOSSLER Switch Operating Mechanism Patent |
| 1931 ANDREW A KRAMER Valve Operating Mechanism Tanks |
| 1931 TRAGER Time Alarm Switch Operating Mechanism |
| 1931 JEFFERSON Railway Switch Operating Art |
| 1931 UNION METAL PROD CO Operating Car Couplers |
| 1931 ARMINGTON Dump Wagon Door Operating Gear |
| 1931 SMALL Device For Operating Car Couplers Art |
| 1931 ARMINGTON Gate Operating Gear Dumping Vehicles |
| 1931 UNION Looper Operating Mechanism Sewing Machines |
| 1931 STREICH BRO A Dump Wagon Door Operating |
| 1931 SINGER Looper Operating Mechanism Sewing Machines |
| 1931 DIEDRICH Operating Bulkhead Doors Art |
| 1931 PALME Looper Operating Mechanism Sewing Machines |
| 1931 STREICH Dump Wagon Door Operating Art |