# Relationship history for MSHA mine 4703192

Current hierarchy: **John  Kolkowski → Sampson Sand & Gravel, Inc. → SAMPSON SAND & GRAVEL**

- 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:** John  Kolkowski → SAMPSON SAND & GRAVEL; 1988-04-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Sampson Sand & Gravel Inc → SAMPSON SAND & GRAVEL; 1999-05-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** John  Kolkowski → Sampson Sand & Gravel Inc; 1999-05-01 to current/open; source msha-controller-operator-history