# Relationship history for MSHA mine 1506711

Current hierarchy: **Hill Doyle → Rockhold Coal Company Inc → Prep Plant**

- 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:** Rockhold Coal Company Inc → Prep Plant; 1950-01-01 to 1978-06-30; source msha-controller-operator-history
- **controller_controls_mine:** Don Lane  Young → Prep Plant; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Don Lane  Young → Rockhold Coal Company Inc; 1950-01-01 to 1978-06-30; source msha-controller-operator-history
- **operator_operates_mine:** Rockhold Coal Company Inc → Prep Plant; 1978-07-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Hill Doyle → Prep Plant; 1978-07-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Hill Doyle → Rockhold Coal Company Inc; 1978-07-01 to current/open; source msha-controller-operator-history