# Relationship history for MSHA mine 3605419

Current hierarchy: **Koppers Company Inc → Nello L Teer Company → Teerco #1 & 2**

- 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:** Nello L Teer Company → Teerco #1 & 2; 1975-01-01 to 1980-05-17; source msha-controller-operator-history
- **controller_controls_mine:** Teer Nello L Company → Teerco #1 & 2; 1975-01-01 to 1980-10-01; source msha-controller-operator-history
- **controller_controls_operator:** Teer Nello L Company → Nello L Teer Company; 1975-01-01 to 1980-05-17; source msha-controller-operator-history
- **operator_operates_mine:** Nello L Teer Company → Teerco #1 & 2; 1980-05-18 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Koppers Company Inc → Teerco #1 & 2; 1980-05-18 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Koppers Company Inc → Nello L Teer Company; 1980-05-18 to current/open; source msha-controller-operator-history