# Relationship history for MSHA mine 0102471

Current hierarchy: **Simmons George M → Berry Mountain Mining Company Inc → Sylvania 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:** Calvert John D → Sylvania Mine; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Calvert & Marsh Coal Company Inc → Sylvania Mine; 1982-05-01 to 1984-02-04; source msha-controller-operator-history
- **controller_controls_operator:** Calvert John D → Calvert & Marsh Coal Company Inc; 1982-05-01 to 1984-02-04; source msha-controller-operator-history
- **controller_controls_mine:** Simmons George M → Sylvania Mine; 1983-06-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Berry Mountain Mining Company Inc → Sylvania Mine; 1984-02-05 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Simmons George M → Berry Mountain Mining Company Inc; 1984-02-05 to current/open; source msha-controller-operator-history