# Relationship history for MSHA mine 3606957

Current hierarchy: **David E  Cook → Ralph M Cook Sand & Gravel → RALPH M. COOK SAND & GRAVEL**

- 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:** Ralph M Cook Sand & Gravel → RALPH M. COOK SAND & GRAVEL; 1980-02-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** David E  Cook  et al → RALPH M. COOK SAND & GRAVEL; 1980-02-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** David E  Cook  et al → Ralph M Cook Sand & Gravel; 1980-02-01 to current/open; source msha-controller-operator-history