# Relationship history for MSHA mine 1510992

Current hierarchy: **Phillips Roy G → Ironwood Coal Company Inc → No 4 Mine**

- 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

- **controller_controls_mine:** Phillips Roy G → No 4 Mine; 1975-11-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Ironwood Coal Company Inc → No 4 Mine; 1978-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Phillips Roy G → Ironwood Coal Company Inc; 1978-01-01 to current/open; source msha-controller-operator-history