# Relationship history for MSHA mine 4001970

Current hierarchy: **Ohio Construction & Engineering Inc & Bagwell Inc → O & B Mining Company → No 3 Surface**

- 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:** O & B Mining Company → No 3 Surface; 1975-02-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Ohio Construction & Engineering Inc & Bagwell Inc → No 3 Surface; 1975-02-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Ohio Construction & Engineering Inc & Bagwell Inc → O & B Mining Company; 1975-02-01 to current/open; source msha-controller-operator-history