# Relationship history for MSHA mine 1512436

Current hierarchy: **Anglo-American Mining Inc → Unity Coal Inc → No 1 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

- **controller_controls_mine:** Ledford Billy J → No 1 Surface; 1976-10-07 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** H R N Coal Company Inc → No 1 Surface; 1980-06-01 to 1981-06-22; source msha-controller-operator-history
- **controller_controls_operator:** Ledford Billy J → H R N Coal Company Inc; 1980-06-01 to 1981-06-22; source msha-controller-operator-history
- **operator_operates_mine:** Unity Coal Company Inc → No 1 Surface; 1981-06-23 to 1982-05-26; source msha-controller-operator-history
- **controller_controls_mine:** Martin Don → No 1 Surface; 1981-06-23 to 1982-05-26; source msha-controller-operator-history
- **controller_controls_operator:** Martin Don → Unity Coal Company Inc; 1981-06-23 to 1982-05-26; source msha-controller-operator-history
- **operator_operates_mine:** Unity Coal Inc → No 1 Surface; 1982-05-27 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Anglo-American Mining Inc → No 1 Surface; 1982-05-27 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Anglo-American Mining Inc → Unity Coal Inc; 1982-05-27 to current/open; source msha-controller-operator-history