# Relationship history for MSHA mine 4609538

Current hierarchy: **Corbin  Robertson III → Quinwood Coal Company LLC → Grassy #1 Surface**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-13T11:19:05.459773+00:00

## Valid-time edges

- **operator_operates_mine:** Quinwood Coal Company LLC → Grassy #1 Surface; 2017-06-13 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Corbin  Robertson III → Grassy #1 Surface; 2017-06-13 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Corbin  Robertson III → Quinwood Coal Company LLC; 2017-06-13 to current/open; source msha-controller-operator-history