# Relationship history for MSHA mine 1510049

Current hierarchy: **Polan William J M → Crest Coal Co Inc → No 5 Surface**

- 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:** Polan William J M → No 5 Surface; 1974-03-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Crest Coal Co Inc → No 5 Surface; 1976-10-15 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Polan William J M → Crest Coal Co Inc; 1976-10-15 to current/open; source msha-controller-operator-history