# Relationship history for MSHA mine 2500768

Current hierarchy: **Yamada Kay → Quality Gravel Company → Minitare 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

- **operator_operates_mine:** Quality Sand & Gravel Company Inc → Minitare Pit; 1950-01-01 to 1978-08-16; source msha-controller-operator-history
- **controller_controls_mine:** Quality Sand & Gravel Company Inc → Minitare Pit; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Quality Sand & Gravel Company Inc → Quality Sand & Gravel Company Inc; 1950-01-01 to 1978-08-16; source msha-controller-operator-history
- **operator_operates_mine:** Quality Gravel Company → Minitare Pit; 1978-08-17 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Yamada Kay → Minitare Pit; 1978-08-17 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Yamada Kay → Quality Gravel Company; 1978-08-17 to current/open; source msha-controller-operator-history