# Relationship history for MSHA mine 4604167

Current hierarchy: **Summerfield A W → Asco Coal Inc → Asco No 1 Mine (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: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **operator_operates_mine:** Asco Coal Inc → Asco No 1 Mine (Surface); 1974-06-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Summerfield A W → Asco No 1 Mine (Surface); 1974-06-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Summerfield A W → Asco Coal Inc; 1974-06-01 to current/open; source msha-controller-operator-history