| 1 | OPPE | OPPEL, F M | | | SCAC4 |
| 2 | OPPI | OPPORTUNITY TRUCKING INC | | | SCAC3 |
| 3 | OPPI | OPTECH INCORPORATED | | | SCAC4 |
| 4 | OPPR | OPPERMAN, HARLAN | | | SCAC3 |
| 5 | OPPR | OPAL RESOURCES CANADA INC | | | SCAC4 |
| 6 | OPPS | ONSITE PETROLEUM PRODUCTS | | | SCAC4 |
| 7 | OPPX | Omaha Public Power District | added 7/1994; 7/2000-7/2005 | | NAKINA |
| 8 | OPPX | Oppenheimer Casing Co. | 7/1932 | | NAKINA |
| 9 | OPPX | Oppenheimer Casing Co. (Union Refrigerator Transit Co.) | 7/1935 | | NAKINA |
| 10 | OPPX | Omaha Public Power District | added 7/94; 7/2000 | | NRHS |
| 11 | OPPX | *OPPENHEIMER CASING CO. | | | PWRC |
| 12 | OPPX | +OMAHA PUBLIC POWER DISTRICT | | | PWRC |
| 13 | OPPX | Omaha Public Power District | | | RSRV |
| 14 | OPPX | OMAHA PUBLIC POWER DISTRICT | | | SCAC4 |
| 15 | OPPZ | OSAGE POWER PLANT | | | PWRC |