# Relationship history for MSHA mine 1508436

Current hierarchy: **Thornberry Danny → Thunderbird Coal Corp → Tunnel Hollow Surface**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-13T11:19:05.459773+00:00

## Valid-time edges

- **operator_operates_mine:** Thunderbird Coal Inc → Tunnel Hollow Surface; 1975-05-01 to 1977-09-15; source msha-controller-operator-history
- **controller_controls_mine:** Worley Oscar → Tunnel Hollow Surface; 1975-05-01 to 1977-09-15; source msha-controller-operator-history
- **controller_controls_operator:** Worley Oscar → Thunderbird Coal Inc; 1975-05-01 to 1977-09-15; source msha-controller-operator-history
- **operator_operates_mine:** Thunderbird Coal Corp → Tunnel Hollow Surface; 1977-09-16 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Thornberry Danny → Tunnel Hollow Surface; 1977-09-16 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Thornberry Danny → Thunderbird Coal Corp; 1977-09-16 to current/open; source msha-controller-operator-history