# Relationship history for MSHA mine 3303291

Current hierarchy: **Williamson Lloyd → S D Nold Company Mining → Hepburn 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

- **operator_operates_mine:** S D Nold Company Mining → Hepburn Strip; 1975-02-21 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Williamson Lloyd → Hepburn Strip; 1975-02-21 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Williamson Lloyd → S D Nold Company Mining; 1975-02-21 to current/open; source msha-controller-operator-history