| 1 | TUGX | Texas Utilities Generating Co. | 1/1980; eliminated 1/1988; 1/1994 | | NAKINA |
| 2 | TUGX | Texas Utilities Mining Co. | added 1/1988; 1/1994-7/2000; eliminated 1/2002 | | NAKINA |
| 3 | TUGX | TXU Mining Co. | added 1/2002; 7/2005; eliminated 1/2008 | | NAKINA |
| 4 | TUGX | Luminant Mining | added 1/2008 | | NAKINA |
| 5 | TUGX | Texas Utilities Generating Co. | 1/80; eliminated 1/88; 1/94 | | NRHS |
| 6 | TUGX | Texas Utilities Mining Co. | added 1/88; 1/94-7/2000 | | NRHS |
| 7 | TUGX | *TXU MINING CO. [TEXAS UTILITIES MINING CO.; TEXAS UTILITIES GENERATING COMPANY] | | | PWRC |
| 8 | TUGX | +LUMINANT MINIMG | | | PWRC |
| 9 | TUGX | Texas Utilities Generating | | | RSRV |
| 10 | TUGX | LUMINANT | | | SCAC4 |
