# Relationship history for MSHA mine 1507634

Current hierarchy: **Lee  Congleton → Richland Coal Company → Nancy 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

- **controller_controls_mine:** Blair Douglas L → Nancy Prep Plant; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Richland Coal Company → Nancy Prep Plant; 1974-10-11 to 1985-09-26; source msha-controller-operator-history
- **controller_controls_operator:** Blair Douglas L → Richland Coal Company; 1974-10-11 to 1985-09-26; source msha-controller-operator-history
- **controller_controls_mine:** Lee  Congleton → Nancy Prep Plant; 1985-09-17 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Richland Coal Company → Nancy Prep Plant; 1985-09-27 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Lee  Congleton → Richland Coal Company; 1985-09-27 to current/open; source msha-controller-operator-history