# Relationship history for MSHA mine 4502519

Current hierarchy: **Asea Brown Boveri Ltd (ABB) → C E Minerals-Combustion Engineering Inc → Calhoun Mill**

- 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:** Boggs Brothers Construction Company → Calhoun Mill; 1950-01-01 to 1981-11-16; source msha-controller-operator-history
- **controller_controls_mine:** Boggs Ray L & Byron E → Calhoun Mill; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Boggs Ray L & Byron E → Boggs Brothers Construction Company; 1950-01-01 to 1981-11-16; source msha-controller-operator-history
- **operator_operates_mine:** C E Minerals-Combustion Engineering Inc → Calhoun Mill; 1981-11-17 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Asea Brown Boveri Ltd (ABB) → Calhoun Mill; 1981-11-17 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Asea Brown Boveri Ltd (ABB) → C E Minerals-Combustion Engineering Inc; 1981-11-17 to current/open; source msha-controller-operator-history