# Relationship history for MSHA mine 4500020

Current hierarchy: **Taiheiyo Cement Corp → Glacier Northwest → Mats Mats 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: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **operator_operates_mine:** Fletcher General Inc → Mats Mats Quarry; 1950-01-01 to 1995-06-30; source msha-controller-operator-history
- **controller_controls_mine:** Fletcher Construction Co (North America) → Mats Mats Quarry; 1950-01-01 to 1995-06-30; source msha-controller-operator-history
- **controller_controls_operator:** Fletcher Construction Co (North America) → Fletcher General Inc; 1950-01-01 to 1995-06-30; source msha-controller-operator-history
- **controller_controls_mine:** Taiheiyo Cement Corp → Mats Mats Quarry; 1988-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Glacier Northwest → Mats Mats Quarry; 1995-07-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Taiheiyo Cement Corp → Glacier Northwest; 1995-07-01 to current/open; source msha-controller-operator-history