# Relationship history for MSHA mine 3606755

Current hierarchy: **Koppers Company Inc → Webster County Coal Company → Teerco 5**

- 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:** Teer Nello L Company → Teerco 5; 1975-01-01 to 1980-10-01; source msha-controller-operator-history
- **operator_operates_mine:** Nello L Teer Company → Teerco 5; 1978-10-01 to 1980-10-01; source msha-controller-operator-history
- **controller_controls_operator:** Teer Nello L Company → Nello L Teer Company; 1978-10-01 to 1980-10-01; source msha-controller-operator-history
- **controller_controls_mine:** Koppers Company Inc → Teerco 5; 1980-08-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Webster County Coal Company → Teerco 5; 1980-10-02 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Koppers Company Inc → Webster County Coal Company; 1980-10-02 to current/open; source msha-controller-operator-history