| 1 | PTOX | PTO Rail, Inc. | 7/2005 (not listed) | | NAKINA |
| 2 | PTOX | PTO, Inc. | added 4/1986; 1/1994-7/2000; eliminated 7/2004 | | NAKINA |
| 3 | PTOX | Pittsburgh-Texas Oil and Gas Co. | 8/1920 | | NAKINA |
| 4 | PTOX | PTO, Inc. | added 4/86; 1/94-7/2000 | | NRHS |
| 5 | PTOX | *PITTSBURGH-TEXAS OIL & GAS CO. | | | PWRC |
| 6 | PTOX | +PTO RAIL, INC. [PTO INCORPORATED] | | | PWRC |
| 7 | PTOX | PTO Rail | | | RSRV |
| 8 | PTOX | PTO RAIL LLC | | | SCAC4 |