# Relationship history for MSHA mine 1502942

Current hierarchy: **Grethel Ridge Coal Company → Grethel Ridge Coal Co → Mine No 2**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **operator_operates_mine:** Grethel Ridge Coal Co → Mine No 2; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Grethel Ridge Coal Company → Mine No 2; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Grethel Ridge Coal Company → Grethel Ridge Coal Co; 1950-01-01 to current/open; source msha-controller-operator-history