# Relationship history for MSHA mine 3503744

Current hierarchy: **Joe A  Kaufman → Sandy's Backhoe & Const. → Libby Creek Quarry**

- 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

- **operator_operates_mine:** Sandy's Backhoe & Const. → Libby Creek Quarry; 2010-04-21 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Joe A  Kaufman → Libby Creek Quarry; 2010-04-21 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Joe A  Kaufman → Sandy's Backhoe & Const.; 2010-04-21 to current/open; source msha-controller-operator-history