# Relationship history for MSHA mine 0100823

Current hierarchy: **Koppers Company Inc → Koppers Company Inc → Woodward 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: 2026-10-13T11:19:05.459773+00:00

## Valid-time edges

- **operator_operates_mine:** Mead Metals & Minerals Inc → Woodward Prep Plant; 1950-01-01 to 1974-10-31; source msha-controller-operator-history
- **controller_controls_mine:** Mead Corp → Woodward Prep Plant; 1950-01-01 to 1974-10-31; source msha-controller-operator-history
- **controller_controls_operator:** Mead Corp → Mead Metals & Minerals Inc; 1950-01-01 to 1974-10-31; source msha-controller-operator-history
- **operator_operates_mine:** Koppers Company Inc → Woodward Prep Plant; 1974-11-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Koppers Company Inc → Woodward Prep Plant; 1974-11-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Koppers Company Inc → Koppers Company Inc; 1974-11-01 to current/open; source msha-controller-operator-history