# Relationship history for MSHA mine 1508184

Current hierarchy: **Bayer William D → Central Elkhorn Mining Company Inc → Prep Plant**

- 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:** Bayer William D → Prep Plant; 1975-02-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Central Elkhorn Mining Company Inc → Prep Plant; 1975-03-31 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Bayer William D → Central Elkhorn Mining Company Inc; 1975-03-31 to current/open; source msha-controller-operator-history