# Relationship history for MSHA mine 4602052

Current hierarchy: **Zeigler Coal Holding Company → Old Ben Coal Company → Mine No 20**

- 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:** British Petroleum Company PLC → Mine No 20; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** United States Steel Mining Company Inc → Mine No 20; 1950-01-01 to 1981-10-27; source msha-controller-operator-history
- **controller_controls_mine:** Usx Corp → Mine No 20; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Usx Corp → United States Steel Mining Company Inc; 1950-01-01 to 1981-10-27; source msha-controller-operator-history
- **operator_operates_mine:** Old Ben Coal Company → Mine No 20; 1981-10-28 to 1990-07-19; source msha-controller-operator-history
- **controller_controls_operator:** British Petroleum Company PLC → Old Ben Coal Company; 1981-10-28 to 1990-07-19; source msha-controller-operator-history
- **controller_controls_mine:** Zeigler Coal Holding Company → Mine No 20; 1985-02-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Old Ben Coal Company → Mine No 20; 1990-07-20 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Zeigler Coal Holding Company → Old Ben Coal Company; 1990-07-20 to current/open; source msha-controller-operator-history