# Relationship history for MSHA mine 3303951

Current hierarchy: **Knowlton W B Jr & D E → Knowltons Industries → Norma (Strip)**

- 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:** Knowlton W B Jr & D E → Norma (Strip); 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Knowltons Industries → Norma (Strip); 1983-09-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Knowlton W B Jr & D E → Knowltons Industries; 1983-09-01 to current/open; source msha-controller-operator-history