# Relationship history for MSHA mine 3500391

Current hierarchy: **Teck Resources Limited → Glenbrook Nickel Company → GLENBROOK NICKEL CO**

- 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:** M A Hanna Company → GLENBROOK NICKEL CO; 1950-01-01 to 1989-04-30; source msha-controller-operator-history
- **controller_controls_mine:** Hanna M A Company → GLENBROOK NICKEL CO; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Hanna M A Company → M A Hanna Company; 1950-01-01 to 1989-04-30; source msha-controller-operator-history
- **operator_operates_mine:** Glenbrook Nickel Company → GLENBROOK NICKEL CO; 1989-05-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Teck Resources Limited → GLENBROOK NICKEL CO; 1989-05-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Teck Resources Limited → Glenbrook Nickel Company; 1989-05-01 to current/open; source msha-controller-operator-history