# Relationship history for MSHA mine 4003597

Current hierarchy: **Don  Robertson → Saltillo Sand and Gravel Inc → Saltillo Sand and 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:** Saltillo Sand and Gravel Inc → Saltillo Sand and Gravel; 2023-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Don  Robertson → Saltillo Sand and Gravel; 2023-05-23 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Don  Robertson → Saltillo Sand and Gravel Inc; 2023-05-23 to current/open; source msha-controller-operator-history