| 1921 DODD ALVIN Audible Signal Patent Print Art |
| 1921 RUSSEL Design Traffic Signal ORSON Patent 49547 |
| 1921 BRADLEY Railway Switch And Signal Patent |
| 1921 BAGNELL Electric Signal Switch Patent Print |
| 1921 ADLER Roadway Crossing Signal Patent Print |
| 1921 KY SWITCH & SIGNAL CO INC Ground Box Patent |
| 1921 FRANK ROME Railroad Signal Patent Print Art |
| 1921 PHILIP Railway Safety Signal Patent Print |
| 1921 RIDOUT Railroad Crossing Signal Patent |
| 1921 ANTON Railroad Crossing Signal Patent Print |
| 1921 FRITZ GRUNIG Block Signal System Patent |
| 1921 MORIN FRANK Fishing Signal Patent Print Art |
| 1921 FESSENDEN Destroy Enemy Guns SIGNAL Patent 22377 |
| 1921 WANKLYN Railway Signal Fusee Patent Print |
| 1921 LAWRENCE Automobile Theft Signal Patent |
| 1921 STEPHENS ROBERT Signal Apparatus Patent |
| 1921 LAWRENCE CURRIE Track Signal Patent Print |
| 1921 ADOLPH PFEIFFER Gong Or Signal Patent Print |
| 1921 MOSES CULBERTSON Train Stop Signal Patent |
| 1921 HOPPE Safety Signal For Street Cars Patent |
| 1921 EMANUEL AUFIERO Warning Signal Patent Print |
| 1921 LOUIS Vehicle Signal Device Patent Print |
| 1921 SMITH SIGNAL CORP Three Way Switch Patent |
| 1921 LESTER Railway Signal System Patent Print |
| 1921 MILLER Railroad Crossing Signal Patent |
| 1921 SCHOOLEY Railway Signal Torpedo Patent |
| 1921 HARKNESS NEWTON Railway Signal Patent Print |
| 1921 ALLEN Railway Signal Device Patent Print |
| 1921 EDGERTON New Design Signal DOUBLE Patent 49594 |
| 1921 MAPEL LEWIS Signal Mechanism Patent Print |
| 1921 HAZAZER EDGAR Electric Signal Patent Print |
| 1921 SADIE WIDEMAN Car Signal Patent Print Art |
| 1921 THOMPSON Ornamental Design Signal Patent 49539 |
| 1921 SUBMARINE SIGNAL CO Stop Clock Patent Print |
| 1921 FRANK Railway Signal Torpedo Patent Print |
| 1921 MCCARTHY DANIEL Signal System Patent Print |
| 1921 MEDEN Design Highway Signal AMERICAN Patent 49559 |
| 1921 PURITON MFG CORP Signal Patent Print Art |
| 1921 RENAULT Train Stop And Signal System Patent |