# Relationship history for MSHA mine 1512627

Current hierarchy: **BHP Billiton → Sierra Coal Company → Prater Branch No 1**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **operator_operates_mine:** Sierra Coal Company → Prater Branch No 1; 1980-11-01 to 1984-04-01; source msha-controller-operator-history
- **controller_controls_mine:** General Electric Company → Prater Branch No 1; 1980-11-01 to 1984-04-01; source msha-controller-operator-history
- **controller_controls_operator:** General Electric Company → Sierra Coal Company; 1980-11-01 to 1984-04-01; source msha-controller-operator-history
- **operator_operates_mine:** Sierra Coal Company → Prater Branch No 1; 1984-04-02 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** BHP Billiton → Prater Branch No 1; 1984-04-02 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** BHP Billiton → Sierra Coal Company; 1984-04-02 to current/open; source msha-controller-operator-history