# Relationship history for MSHA mine 4604656

Current hierarchy: **Massey Energy Company → Alpine Development 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:** Hawley Charbon → Mine No 20; 1974-11-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** No 10 Coal Mine Inc → Mine No 20; 1975-09-01 to 1985-09-06; source msha-controller-operator-history
- **controller_controls_operator:** Hawley Charbon → No 10 Coal Mine Inc; 1975-09-01 to 1985-09-06; source msha-controller-operator-history
- **controller_controls_mine:** Massey Energy Company → Mine No 20; 1985-07-15 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Alpine Development Company → Mine No 20; 1985-09-07 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Massey Energy Company → Alpine Development Company; 1985-09-07 to current/open; source msha-controller-operator-history