# Relationship history for MSHA mine 4703225

Current hierarchy: **Paul  Duffek; Calvin  Krueger → Duffek Sand & Gravel Inc → POWER SCREEN**

- 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

- **controller_controls_mine:** Calvin  Krueger  et al → POWER SCREEN; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Duffek Sand & Gravel Inc → POWER SCREEN; 1999-11-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Calvin  Krueger  et al → Duffek Sand & Gravel Inc; 1999-11-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Paul  Duffek  et al → Duffek Sand & Gravel Inc; 1999-11-01 to current/open; source msha-controller-operator-history