# Relationship history for MSHA mine 4702507

Current hierarchy: **Paul  Duffek; Calvin  Krueger → Duffek Sand & Gravel Inc → Duffek Sand & Gravel Pits Evert Col**

- 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

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