# Relationship history for MSHA mine 3606073

Current hierarchy: **Hamer Ardell B → Ardell B Hamer Coal & Clay → Hamer #2 Strip Mine**

- 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:** Hamer Ardell B → Hamer #2 Strip Mine; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Ardell B Hamer Coal & Clay → Hamer #2 Strip Mine; 1976-06-21 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Hamer Ardell B → Ardell B Hamer Coal & Clay; 1976-06-21 to current/open; source msha-controller-operator-history