# Relationship history for MSHA mine 2100249

Current hierarchy: **National Steel Corp → National Steel Pellet Company → NAT'L STEEL PELLET CO (MINE)**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-18T09:31:49.615908+00:00

## Valid-time edges

- **operator_operates_mine:** M A Hanna Company → NAT'L STEEL PELLET CO (MINE); 1950-01-01 to 1988-12-31; source msha-controller-operator-history
- **controller_controls_mine:** Hanna M A Company → NAT'L STEEL PELLET CO (MINE); 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 1988-12-31; source msha-controller-operator-history
- **operator_operates_mine:** National Steel Pellet Company → NAT'L STEEL PELLET CO (MINE); 1989-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** National Steel Corp → NAT'L STEEL PELLET CO (MINE); 1989-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** National Steel Corp → National Steel Pellet Company; 1989-01-01 to current/open; source msha-controller-operator-history