# Relationship history for MSHA mine 4503492

Current hierarchy: **Lafarge S A → Friday Harbor Sand & Gravel Co. → Friday Harbor S&G Co-Killam Pit**

- 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

- **controller_controls_mine:** Lafarge S A → Friday Harbor S&G Co-Killam Pit; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Friday Harbor Sand & Gravel Co. → Friday Harbor S&G Co-Killam Pit; 2001-09-16 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Lafarge S A → Friday Harbor Sand & Gravel Co.; 2001-09-16 to current/open; source msha-controller-operator-history