# Relationship history for MSHA mine 0102459

Current hierarchy: **Calvert John D → Calvert & Marsh Coal Company Inc → Margaret**

- 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

- **controller_controls_mine:** Calvert John D → Margaret; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Calvert & Marsh Coal Company Inc → Margaret; 1982-03-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Calvert John D → Calvert & Marsh Coal Company Inc; 1982-03-01 to current/open; source msha-controller-operator-history