# Relationship history for MSHA mine 4201716

Current hierarchy: **Gordon S  Ziegler Jr → Ziegler Chemical & Mineral Corp → Bonanza #12 Shaft**

- 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:** Gordon S  Ziegler Jr → Bonanza #12 Shaft; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Ziegler Chemical & Mineral Corp → Bonanza #12 Shaft; 1981-02-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Gordon S  Ziegler Jr → Ziegler Chemical & Mineral Corp; 1981-02-01 to current/open; source msha-controller-operator-history