# Relationship history for MSHA mine 4001757

Current hierarchy: **Byrd Oliver & Roger → Byrd & Son Coal Company → No 1 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: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **operator_operates_mine:** Byrd & Son Coal Company → No 1 Mine; 1975-04-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Byrd Oliver & Roger → No 1 Mine; 1975-04-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Byrd Oliver & Roger → Byrd & Son Coal Company; 1975-04-01 to current/open; source msha-controller-operator-history