# Relationship history for MSHA mine 4604742

Current hierarchy: **Nippon Kokan K K → National Mines Corp → Douglas 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:** Nippon Kokan K K et al → Douglas Prep Plant; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Carroll Preston W → Douglas Prep Plant; 1973-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Iaeger Mining Company Inc → Douglas Prep Plant; 1975-06-16 to 1977-07-01; source msha-controller-operator-history
- **controller_controls_operator:** Carroll Preston W → Iaeger Mining Company Inc; 1975-06-16 to 1977-07-01; source msha-controller-operator-history
- **operator_operates_mine:** National Mines Corp → Douglas Prep Plant; 1977-07-02 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Nippon Kokan K K et al → National Mines Corp; 1977-07-02 to current/open; source msha-controller-operator-history