# Relationship history for MSHA mine 3600102

Current hierarchy: **Grings Ralph D & John A → Grings Quarry → Grings Quarry Sandstone Operation**

- 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:** Grings Quarry → Grings Quarry Sandstone Operation; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Grings Ralph D & John A → Grings Quarry Sandstone Operation; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Grings Ralph D & John A → Grings Quarry; 1950-01-01 to current/open; source msha-controller-operator-history