# Relationship history for MSHA mine 3401219

Current hierarchy: **Brooksher Keith → Al'S Tractor & Backhoe Service → Smith Pit**

- 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:** Yarbrough Sand & Gravel Company → Smith Pit; 1979-07-01 to 1983-03-15; source msha-controller-operator-history
- **controller_controls_mine:** Yarbrough William W → Smith Pit; 1979-07-01 to 1983-03-15; source msha-controller-operator-history
- **controller_controls_operator:** Yarbrough William W → Yarbrough Sand & Gravel Company; 1979-07-01 to 1983-03-15; source msha-controller-operator-history
- **operator_operates_mine:** Al'S Tractor & Backhoe Service → Smith Pit; 1983-03-16 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Brooksher Keith → Smith Pit; 1983-03-16 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Brooksher Keith → Al'S Tractor & Backhoe Service; 1983-03-16 to current/open; source msha-controller-operator-history