# Relationship history for MSHA mine 3607991

Current hierarchy: **Nyswaner Robert E → American Coal Company → Snyder Strip**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-18T09:31:49.615908+00:00

## Valid-time edges

- **controller_controls_mine:** Nyswaner Robert E → Snyder Strip; 1983-04-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** American Coal Company → Snyder Strip; 1988-02-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Nyswaner Robert E → American Coal Company; 1988-02-01 to current/open; source msha-controller-operator-history