# Relationship history for MSHA mine 2500939

Current hierarchy: **Davidson K L → Davidson Sand & Gravel Company → Davidson Pit & Plant**

- 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:** Davidson Sand & Gravel Company → Davidson Pit & Plant; 1979-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Davidson K L → Davidson Pit & Plant; 1979-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Davidson K L → Davidson Sand & Gravel Company; 1979-01-01 to current/open; source msha-controller-operator-history