# Relationship history for MSHA mine 4201624

Current hierarchy: **Wirthlin Robert L → General Rock Products Corp → General Rock Products #3**

- 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:** Wirthlin Robert L → General Rock Products #3; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** General Rock Products Corp → General Rock Products #3; 1979-10-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Wirthlin Robert L → General Rock Products Corp; 1979-10-01 to current/open; source msha-controller-operator-history