# Relationship history for MSHA mine 3303666

Current hierarchy: **Birchfield Robert → Coal Resources → Coal Resources Strip**

- 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:** Coal Resources → Coal Resources Strip; 1977-12-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Birchfield Robert → Coal Resources Strip; 1977-12-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Birchfield Robert → Coal Resources; 1977-12-01 to current/open; source msha-controller-operator-history