# Relationship history for MSHA mine 1200371

Current hierarchy: **William  Robertson; Katherine  Robertson → Robertson Crushed Stone Inc → Milltown Rock Quarry**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-13T11:19:05.459773+00:00

## Valid-time edges

- **operator_operates_mine:** Robertson Crushed Stone Inc → Milltown Rock Quarry; 1979-05-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Charles P  Robertson → Milltown Rock Quarry; 1979-05-01 to 2024-12-31; source msha-controller-operator-history
- **controller_controls_operator:** Charles P  Robertson → Robertson Crushed Stone Inc; 1979-05-01 to 2024-12-31; source msha-controller-operator-history
- **controller_controls_mine:** William  Robertson et al → Milltown Rock Quarry; 2025-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** William  Robertson et al → Robertson Crushed Stone Inc; 2025-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Katherine  Robertson et al → Robertson Crushed Stone Inc; 2025-01-01 to current/open; source msha-controller-operator-history