# Relationship history for MSHA mine 1502810

Current hierarchy: **Haywood Billy H → One-A Coal Company Inc → Mine #1**

- 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:** National Mines Corp → Mine #1; 1950-01-01 to 1983-03-22; source msha-controller-operator-history
- **controller_controls_mine:** Nippon Kokan K K et al → Mine #1; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Nippon Kokan K K et al → National Mines Corp; 1950-01-01 to 1983-03-22; source msha-controller-operator-history
- **operator_operates_mine:** One-A Coal Company Inc → Mine #1; 1983-03-23 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Haywood Billy H → Mine #1; 1983-03-23 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Haywood Billy H → One-A Coal Company Inc; 1983-03-23 to current/open; source msha-controller-operator-history