| 1 | RPCX | Railroad Passenger Car Numbering Bureau Inc. | 7/2005 (not listed) | | NAKINA |
| 2 | RPCX | Robeson Process Co. | 8/1920-10/1966; eliminated 10/1969 | | NAKINA |
| 3 | RPCX | Ralston Purina Co. | added 1/1974; 1/1975-1/1980; eliminated 7/1989 | | NAKINA |
| 4 | RPCX | Robeson Process Co. | 4/38-10/66; eliminated 10/69 | | NRHS |
| 5 | RPCX | Ralston Purina Co. | added 1/74; 1/75-1/80; eliminated 7/89 | | NRHS |
| 6 | RPCX | *ROBESON PROCESS CO. | | | PWRC |
| 7 | RPCX | *RALSTON PURINA CO. | | | PWRC |
| 8 | RPCX | +RAILROAD PASSENGER CAR NUMBERING BUREAU, INC. | | | PWRC |
| 9 | RPCX | Railroad Passenger Car Numbering Bureau | | | RSRV |
| 10 | RPCX | RAILROAD PASSENGER CAR NUMBERING BU | | | SCAC4 |
| 11 | RPCX | Ralston Purina Co. | | USA | TRAFFIC |
